... ADP023770. Title : ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys. Descriptive Note : Conference paper. ...
DTIC Science & Technology
... Title : Ab-Initio Molecular Dynamics Simulations of Molten Ni-Based Superalloys. Descriptive Note : Conference paper (preprint). ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... Title : Ab-Initio Molecular Dynamics Simulations ...
control of molecular dynamics; grid methods in the solution of time-dependent problems in quantum mechanics; ab initio calculation of potential energy surfaces and vibronic...
Science.gov Websites
An ab initio centroid molecular dynamics (CMD) method is developed by combining the CMD method with the ab initio molecular orbital method. The ab initio CMD method is applied to vibrational dynamics of diatomic molecules, H2 and ...
NASA Astrophysics Data System (ADS)
In this work, we present a study on water acetonitrile (AN) mixtures by molecular dynamics ab initio and X-ray diffraction techniques. Comparison of the experimental total G(r) functions of the mixtures with the results of molecular dynamics simulation shows an overall good ...
materials, (iiii) phonon recycling in lasers, and (iv) phonon-assisted photon absorption in photovoltaics. The theoretical treatments include ab initio and molecular dynamic...
In this review we present the techniques of ab initio molecular dynamics simulation improved to its current stage where the analysis of existing processes and the prediction of further chemical features and real-world processes are feasible. For this reason we describe the relevant developments in ...
PubMed
... For example, ab initio quantum chemical calculations when combined with reaction rate theory and kinetics modeling can, in principle, be capable ...
... 3. Ab initio calculations on ammonia, formamide, pyrrole and pyridine. ... The results given in Appendix II for formamide (HCONH2) are typical of the ...
., Montcourier, P., and Fort, P. (1998). RhoG GTPase controls a pathway that independently activates Rac1 and Cdc
E-print Network
................................................................................ 36 5. Glyoxal as a source of organic aerosol
... At present experimental data for ternary Ni-Al-W alloys is not available, and estimates of the accuracy of the Mukai model for liquid density in this ...
... dependent densities in the multicomponent RENE-N4 superalloy, and estimates of the accuracy of the Mukai model for liquid density in this system ...
Inelastic neutron scattering, density functional theory, ab initio molecular dynamics, and classical molecular dynamics were used to examine the behavior of nanoconfined water in palygorskite and sepiolite. These complementary methods provide a strong bas...
National Technical Information Service (NTIS)
) to applied external force. We first investigate the mechanical response using an ab initio molecular dynamics where the reaction path depends on the strength and nature of the applied force. We first investigate the response of CB under applied forces using steered molecular ...
Electrical conductivity data of Al for the densities from normal to a fraction of normal density and temperatures up to a few thousand Kelvin are important inputs for the hydrodynamic simulations of exploding aluminium foils. We have generated conductivity data of aluminium, by using ab-initio molecular dynamics simulations and the ...
and O�H bond length for a simple water molecule and for water in contact with NaCl surfaces. The resultsAB INITIO MOLECULAR�DYNAMICS SIMULATIONS OF ADSORPTION OF DYE MOLECULES AT SURFACES M. SUGIHARA, H molecules on the NaCl(100) surface. The investigations concentrate on the flat dye molecules trimethin, [C
A biased potential molecular dynamics simulation approach, accelerated molecular dynamics (AMD), has been implemented in the framework of ab initio molecular dynamics for the study of chemical reactions. Using two examples, the ...
with molecular dynamic simulations in combination with high level correlated ab initio quantum chemical the existing minima in the PES. 2. Ab initio quantum-chemical calculations. The lowest energy minima (within surface analysis by metadynamics. Gibbs energies and ...
NMR chemical shifts for an L-alanine molecular crystal are calculated using ab initio plane wave density functional theory. Dynamical effects including anharmonicity may be included by averaging chemical shifts over an ensemble of structural configurations generated using molecular dynamics (MD). The time scales ...
The high-pressure induced phase transformation from the zinc blende to rocksalt structure in SiC has been studied by the ab initio molecular dynamics method. The simulations showed that SiC passes through a tetragonal intermediate state before transforming to a monoclinic phase at 160�GPa. The mechanism for this ...
We introduce an ab initio molecular-dynamics method based on the discretized path-integral representation of quantum particles. Fermi statistics is automatically generated by an effective exchange potential. This path-integral molecular-dynamics method is able to simulate electron plasmas at the border of the ...
Mass tensor molecular dynamics method was first introduced by Bennett [J. Comput. Phys. 19, 267 (1975)] for efficient sampling of phase space through the use of generalized atomic masses. Here, we show how to apply this method to ab initio molecular dynamics simulations ...
Research completed during the period 1 Feb. 1990 - 28 Feb. 1994 is summarized in the following included papers: 'Ab Initio Statistical Mechanics of Structural Phase Transition'; 'Ab Initio Molecular Dynamics: Analytically Continued Energy Functionals and Insights into ...
We perform ab initio molecular dynamics simulations to study the dissociation of NaCl in water. The potential of mean force (PMF) between the two ions is determined using the constrained-force method. The simulation windows corresponding to the contact and solvent-separated minima, and the transition state in ...
-wave /pseudopotential codes [2,5�7]. Parallelization of the CPMD code was done on different levels. The central-initio Molecular Dynamics: Reaching Teraflop Performance with the CPMD Code J�urg Hutter Physical Chemistry-level Parallelism for ab-initio Molecular ...
The methodology of ab initio molecular dynamics, wherein finite-temperature dynamical trajectories are generated by using forces computed "on the fly" from electronic structure calculations, has had a profound influence in modern theoretical research. Ab initio ...
The methodology of ab initio molecular dynamics, wherein finite-temperature dynamical trajectories are generated by using forces computed �on the fly� from electronic structure calculations, has had a profound influence in modern theoretical research. Ab initio ...
PubMed Central
We present results for the static and dynamic structural properties of undercooled liquid Si, at several temperatures between 1550 K and 1100 K, obtained through orbital-free ab-initio molecular dynamics simulations. The local bond angle distributions show a modest increase in the tetrahedral order upon decreasing the temperature. We ...
Structural and spectroscopic properties of hydrazine, H(2)N-NH(2), it being a floppy or fluxional molecule in a vacuum, are investigated by means of ab initio molecular dynamics, ab initio path integral molecular dynamics, and ...
The near-UV absorption spectra of barnase double-point mutants are calculated using a combination of molecular dynamics and ab initio techniques. The atoms of the fluorescent probes are placed in a cloud of point charges, generated by molecular dynamics simulations. ...
Molecular dynamics (MD) is a powerful tool to probe the thermodynamic and kinetic properties of solid, glass and liquid phases. In classical molecular dynamics (CMD), empirical models are used to describe the force by considering bond, bend and dihedral angle contributions with parameters fitted to experimental ...
Energy Citations Database
... The work presented here makes use of state-of- validated mathematical criteria for predicting the-art AIMD simulations as a means for testing the ...
This bibliography lists the following reports: Optimized pseudopotentials, Ab-initio materials science and engineering using the molecular dynamics methods for total energy pseudopotential calculations, Oxygen complexes in Si, The enchanting properties of...
This report briefly summarizes the research developments in ab initio dynamics made possible by this augmentation award to the parent ONR grant. A full description of the research accomplishments will appear in the final technical report of the parent gra...
We present a combined experimental and theoretical study on carbon nanodiamonds using Raman and DAC experimentation and ab initio calculations. Our calculations confirm the surface reconstruction to a fullerene-like structure, and indicate compression of ...
The content of an ab-initio time-dependent theory of quantum molecular dynamics of electrons and atomic nuclei is presented. Employing the time-dependent variational principle and a family of approximate state vectors yields a set of dynamical equations a...
The fundamental nature of the research was exemplified by ab-initio predictions of the friction coefficient of single crystal diamond sliding against its mating diamond plane, and molecular dynamics calculations on single crystal calcium fluoride and bari...
The theoretical principles underpinning the calculation of infrared spectra for condensed-phase systems in the context of ab initio molecular dynamics have been recently developed in literature. At present, most ab initio molecular ...
The predicted high pressure superionic phases of water and HF are investigated via ab initio molecular dynamics. These phases could potentially be achieved through either static compression with heating or through shock compression. We study water at dens...
Atom-centered partial charges are calculated for the Fe-heme in cytochrome P450cam for use in molecular dynamics simulations of polar substrates bound in the active site of the enzyme. Charges are fit to the electrostatic potential produced by ab initio U...
With the development of ab-initio molecular dynamics method, it has now become possible to study the static and dynamical properties of clusters containing up to a few tens of atoms. Here I present a review of the method within the framework of the densit...
�O liquids11,12 . The calcula- tions were done using the software package VASP24 , which is exceptionally ef
The protonation scheme and the hydrogen bond connectivity in the structure of jennite were investigated by ab initio molecular dynamics simulations. The calculated statistics of hydrogen bonds at ambient conditions is consistent with the protonation scheme proposed by Bonaccorsi et al. (2004) based on the bond ...
High-pressure induced zinc blende to rocksalt phase transition in GaN has been investigated by ab initio molecular dynamics method to characterize the transformation mechanism at the atomic level. It was shown that at 100 GPa GaN passes through tetragonal and monoclinic states before rocksalt structure is formed. ...
We have developed an ab initio path integral molecular dynamics method based on the fragment molecular orbital method. This �FMO-PIMD� method can treat both nuclei and electrons quantum mechanically, and is useful to simulate large hydrogen-bonded systems with high accuracy. After a benchmark calculation for ...
The decomposition of ethylene carbonate (EC) during the initial growth of solid-electrolyte interphase (SEI) films at the solvent-graphitic anode interface is critical to lithium ion battery operations. Ab initio molecular dynamics simulations of explicit liquid EC/graphite interfaces are conducted to study these ...
The fully ionized (metallic) hydrogen plasma is studied by [ital ab] [ital initio] molecular dynamics simulations, for classical protons and fully degenerate electrons, in the strong coupling regime of the protons. The calculated ion-electron pair distribution function signals the breakdown of linear screening with ...
Ab initio molecular dynamics simulations of a recently proposed cobalt-based catalyst for water oxidation provide insight into the properties of protons at the water/oxide interface. Calculations and X-ray absorption spectroscopy data indicate a cubane-like structure of the catalyst, support the occurrence of ...
A comprehensive study of static, dynamic and electronic properties of liquid Al in a thermodynamic state near its triple point was performed by means of 205-particle ab initio molecular dynamics simulations using Kohn-Sham density-functional theory and the Langevin equation of motion. The good agreement of the ...
Density functional theory based ab initio molecular dynamics simulations with explicit inclusion of empirical van der Waals (vdW) corrections of supercritical carbon dioxide have been performed. Significant changes in the intermolecular pair correlation functions of the fluid modeled with the added vdW interactions ...
The relaxation of hot hydrogen atoms upon the dissociative adsorption of H2 on Pd(100) was studied by ab initio molecular dynamics simulations based on density functional theory, modeling the full dissociative adsorption process in a consistent manner. In spite of the nonlinear dependence of every single trajectory ...
An outstanding problem in the computer-based microscopic description of Group IV materials, is the need for an accurate transferable model of the energetic and electronic properties of semiconductor structures. The three complementary approaches have been the ab-initio method including Car-Parinello simulations, the classical molecular ...
We present a microscopic model of the interaction and adsorption mechanism of simple organic molecules on SiC surfaces as obtained from ab initio molecular dynamics simulations. Our results open the way to functionalization of silicon carbide, a leading candidate material for bio-compatible devices.
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scaling DFT code (see Peter Haynes) Other codes used in TCM for applications ffl CPMD � DFT ab initio? (MT/RN) ffl non�collinear spins in QMC (MT) ffl Pseudopotentials for many�body calculations (Lee, Mostofi, Di'eguez) Applications etc..(CASTEP, CPMD) ffl ab initio molecular ...
,3 While much is known about the properties of the low energy NaCl(001) surface and water covered NaCl(001 the properties of ambient liquid water films remains a challenge for both experiment and first the properties of the hitherto mysterious nanoscale water film that covers NaCl(001). From our ab initio
The recent literature on the determination of minimum energy conformations by ab initio quantum mechanical techniques is reviewed. The availability of computer-coded analytical first and second derivatives of the Hartree-Fock energy makes possible calculations that will be of significant assistance in structure determination of molecules. A short review of ...
We present a formulation of ab initio electronic structure calculations in a finite magnetic field, which retains the simplicity and efficiency of techniques widely used in first principles molecular dynamics simulations, based on plane-wave basis sets and Fourier transforms. In addition we discuss results obtained ...
Ab initio molecular dynamics is used to compute the thermal conductivity of hydrogen at 80 g cm{sup -3} and temperature up to 800 eV. Pressures and ionic structure are compared with orbital-free calculations. Thermal conductivity is evaluated using the Kubo-Greenwood formula and is compared with models currently ...
and compression cycles is studied. Ab-initio local- spin-density functional based molecular dynamics simula- tions the Born-Oppenheimer Local-Spin-Density Functional Molecular-Dynamics (BO-LSD-MD) method [28] in inves confining the electrons in the wire is short-ranged (as also found in recent local density ...
Studies of ring-saturated pyrimidine base lesions are used to illustrate an integrated modeling approach that combines quantum-chemical calculations with molecular dynamics simulation. Electronic-structure calculations on the lesions in Isolation reveal s...
The aim of this thesis is to study metallic sodium clusters by numerical simulation. We have developed two ab initio molecular dynamics programs within the formalism of density functional theory. The first is based on the semi- classical extended Thomas-F...
: the four bead model A(1-40) and A(1-42) oligomer formation -four-bead protein model with amino acid of electrostatic interactions in A oligomer formation: A discrete molecular dynamics study,'' in preparation: The DMD code has been generalized to account for assembly studies of two different peptides. Oligomer
Momentum imaging experiments on dissociative electron attachment to the water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via ...
Momentum imaging experiments on dissociative electron attachment (DEA) to a water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via ...
. All ab initio molecular dynamics simulations were performed with the CPMD program.13 Density func and Ernzerhof.14 Core electrons on all atoms were represented by norm- conserving pseudopotentials15). 13 J. H�utter et al., CPMD, Copyright IBM Z�urich Research Laboratory and MPI f�ur Festk
The Born-Oppenheimer approximation divides the problem of quantum molecular dynamics into two familiar problems: (1) solution for the electronic wave functions for a given instantaneous arrangement of ions and (2) the motion of the atomic cores under the ...
The nature of intermolecular interactions between aromatic amino acid residues has been investigated by a combination of molecular dynamics and ab initio methods. The potential energy surface of various interacting pairs, including tryptophan, phenilalanine, and tyrosine, was scanned for determining all the ...
Recent progress in the ab-initio molecular dynamics method and the power of parallel computing, allow the detailed study of complex chemical reaction of great industrial relevance. We illustrate this unprecedented capability by investigating the second generation Ziegler-Natta catalytic process. In this inhomogeneous catalyst, a ...
An ab initio molecular dynamics (MD) simulation technique employing the Born-Oppenheimer approach in the framework of a Gaussian implementation of Kohn-Sham density functional theory is used to study the gas-phase conformational dynamics of an alanine dipeptide analog. It is found that conformational transformation ...
We build an "all-electron" norm-conserving pseudopotential for boron which extends the use of ab initio molecular dynamics simulations up to 50 times the normal density rho0. This allows us to perform ab initio simulations of dense plasmas from the regime where quantum ...
We build an 'all-electron' norm-conserving pseudopotential for boron which extends the use of ab initio molecular dynamics simulations up to 50 times the normal density {rho}{sub 0}. This allows us to perform ab initio simulations of dense plasmas from the ...
The high-pressure induced phase transformation from the zinc blende to rocksalt structure in SiC has been studied by ab initio molecular dynamics. The simulations show that SiC passes through tetragonal and then monoclinic intermediate states before finally forming the rock salt structure at 160 GPa. The mechanism ...
We report herein a series of ab initio simulations of water under both static and shocked conditions. We have calculated the coherent x-ray scattering intensity of several phases of water under high pressure, using ab initio Density Functional Theory (DFT). We provide new atomic scattering form factors for water at ...
We develop a strategy based on a molecular dynamics method with reactive force fields for large-scale simulations of reacting systems. The considerably enhanced computational efficiency (105 times faster than an ab initio molecular dynamics method) opens an avenue to ...
The conformational preference of the glycosidic linkage of methyl-?-mannose was studied in the gas phase and in aqueous solution by ab initio calculations, and by molecular dynamics (MD) and Car-Parrinello molecular dynamics (CPMD) simulations. MD simulations were performed ...
The gas phase reaction of Th(+) with H(2)O to produce HThO(+) + H and ThO(+) + H(2) was investigated using density functional theory and coupled cluster methods. RRKM calculations of the branching ratio favor the H atomic elimination channel in disagreement with experiment. Ab initio classical trajectory calculations were carried out to obtain a better ...
An all-atom force field for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is presented. The classical intermolecular interaction potential for TATB is based on single-point energies determined from high-level ab initio calculations of TATB dimers. The newly developed potential function is used to examine bulk crystalline TATB via ...
Classical molecular dynamics (CMD) calculations are fast but are heavily dependent on the potential feasibility. On the other hand, first-principles (ab initio) molecular dynamics (AIMD) does not use any empirical knowledge, but can be extremely time consuming. As both ...
Born-Oppenheimer ab initio QM/MM molecular dynamics simulation with umbrella sampling is a state-of-the-art approach to calculate free energy profiles of chemical reactions in complex systems. To further improve its computational efficiency, a mass-scaling method with the increased time step in MD simulations has ...
The ab initio molecular-dynamics formalism of Car and Parrinello is extended to preserve the locality of the orbitals. The supplementary term in the Lagrangian does not affect the nuclear dynamics, but ensures "on the fly" localization of the electronic orbitals within a periodic supercell in the Gamma-point approximation. The ...
The ab initio molecular-dynamics formalism of Car and Parrinello is extended to preserve the locality of the orbitals. The supplementary term in the Lagrangian does not affect the nuclear dynamics, but ensures ``on the fly'' localization of the electronic orbitals within a periodic supercell in the ?-point approximation. The ...
Pairing of guanidinium moieties in water is explored by molecular dynamics simulations of short arginine-rich peptides and ab initio calculations of a pair of guanidinium ions in water clusters of increasing size. Molecular dynamics simulations show that, in an aqueous ...
Ab initio molecular dynamics simulations are a powerful tool for examining liquids and amorphous materials; however, such simulations are often computationally intensive. We present a molecular dynamics method that dramatically reduces the computational load using a new ...
For the equilibrium immiscible Fe-Cu system, ab initio calculations using the projector augmented wave method identify the relatively stable structures of the metastable Fe25Cu75 and Fe50Cu50 alloys to be both of fcc and determine their corresponding lattice constants and cohesive energies. Some of the ab initio ...
In this paper (paper I) and the following paper (paper II) [C. Bratschi, H. Huber, and D. J. Searles, J. Chem. Phys. 126, 164105 (2007)], a new molecular dynamics algorithm implementing the Gibbs ensemble will be presented and then on applied to the liquid-vapor coexistence curve for two ab initio CO2 potentials. ...
Decomposition of energetic molecules such as pentaerythritol tetranitrate is accompanied by extensive changes in their electronic configuration and thus is challenging for ab initio Born-Oppenheimer molecular dynamics simulations. The performance of single-determinant methods (in particular, density-functional ...
of the BCB moiety) to applied external force. We first investigate the mechanical response using an ab initio mechanophores where the reaction path depends on the strength and nature of the applied force. We first investigate the response of CB under applied forces using steered molecular dynamics8 (SMD) combined ...
We have developed new force field and parameters for copper(I) and mercury(II) to be used in molecular dynamics simulations of metalloproteins. Parameters have been derived from fitting of ab initio interaction potentials calculated at the MP2 level of theory, and results compared to experimental data when ...
The use of discrete variable representation (DVR) basis sets within ab initio molecular dynamics calculations allows the latter to be performed with converged energies and, more importantly, converged forces. In this paper, we show how to carry out ab initio ...
In a previous contribution, we outlined a method for predicting (hydr)oxy-acid and oxide surface acidity constants based on three main factors: bond valence, Me O bond ionicity, and molecular shape. Here, electrostatics calculations and ab initio molecular dynamics simulations are used to qualitatively show that Me ...
A multiscale technique is developed that couples empirical molecular dynamics (MD) and ab�initio density functional theory (DFT). An overlap handshaking region between the empirical MD and ab�initio DFT regions is formulated and the interaction forces between the carbon atoms are calculated based on the ...
Ab initio molecular dynamics (MD) method has been used to study high pressure-induced phase transformation in BeO based on the local density approximation (LDA) and the generalized gradient approximation (GGA). Both methods show that the wurtzite (WZ) and zinc blende (ZB) BeO transforms to the rocksalt (RS) ...
Social permutation invariant coordinates are introduced describing the bond network around a given atom. They originate from the largest eigenvalue and the corresponding eigenvector of the contact matrix, are invariant under permutation of identical atoms, and bear a clear signature of an order-disorder transition. Once combined with ab�initio metadynamics, these coordinates ...
Simulations of the tetravalent group IV metal ions, Ge(IV), Sn(IV), and Pb(IV), in aqueous solution were performed using ab initio quantum mechanical charge field molecular dynamics (QMCF MD). The process of hydrolysis, which occurred for each of the metal ions, was analyzed in terms of the time evolution of ...
Social permutation invariant coordinates are introduced describing the bond network around a given atom. They originate from the largest eigenvalue and the corresponding eigenvector of the contact matrix, are invariant under permutation of identical atoms, and bear a clear signature of an order-disorder transition. Once combined with ab initio ...
Molecular dynamics simulations were performed using a modified amoeba force field to determine hydration and dynamical properties of the divalent cations Ca2+ and Mg2+. The extension of amoeba to divalent cations required the introduction of a cation specific parametrization. To accomplish this, the Thole polarization damping model parametrization was ...
Molecular dynamics simulations were performed using a modified amoeba force field to determine hydration and dynamical properties of the divalent cations Ca2+ and Mg2+. The extension of amoeba to divalent cations required the introduction of a cation specific parametrization. To accomplish this, the Thol� polarization damping model parametrization was ...
The four possible mechanisms of ring closure in dioxin formation from chlorophenols are studied using ab initio molecular dynamics, within generalized gradient approximation. Free energy barriers, derived as the potential of mean constraint force, directly lead to a static approximation for the transition rates. We ...
Using ab initio molecular dynamics we investigate the electronic and lattice structure of AFe2As2 (A=Ca,Sr,Ba) under pressure. We find that the structural phase transition (orthorhombic to tetragonal symmetry) is always accompanied by a magnetic phase transition in all the compounds while the nature of the ...
We present results for several structural and dynamical properties of the liquid Li1-xNax alloy. The study has been carried out by means of the orbital-free ab initio molecular dynamics method, combined with local ionic pseudopotentials constructed within the same framework. We obtain good agreement with the ...
The structural and bonding properties of liquid boron oxide are studied by ab initio molecular dynamics simulations. It is seen that, even in the liquid state, boron atoms are predominantly threefold coordinated to oxygen atoms, and most of oxygen atoms bridge two adjacent boron atoms. The neighboring atoms are ...
The initial stages of NaCl dissolution in liquid water have been examined with state-of-the-art ab initio molecular dynamics and free energy sampling techniques. Our simulations reveal a complex multi-step process triggered by the departure of Cl ions from the lattice, with a well-defined intermediate state wherein ...
The accurate molecular simulation of many hydrated chemical systems, including clay minerals and other phyllosilicates and their interfaces with aqueous solutions, requires improved classical force field potentials to better describe structure and vibrational behavior. Classical and ab initio molecular dynamics ...
Potassium ion in water plays a very important role in chemistry and biology. In this paper, we investigated the hydration structure and coordination of K(+) solvation in water at 300 and 450 K using ab initio Car-Parrinello molecular dynamics. The K(+)-oxygen radial distribution function indicated that the ...
An overview of the parallel algorithms for ab initio molecular dynamics (AIMD) used in the NWChem program package is presented, including recent developments for computing exact exchange. These algorithms make use of a two-dimensional processor geometry proposed by Gygi et al for use in AIMD algorithms. Using this ...
An aqueous glycine solution is studied with ab initio molecular dynamics to investigate the structural aspects of the different solvation shells within the zwitterion and their impact on the infrared spectrum. The individual contributions to the total IR spectrum from glycine and solvation water are decomposed ...
The local atomic structure and elastic properties of two series of multicomponent amorphous steels--with and without phosphorus addition--have been investigated by ab initio molecular dynamics. A comparison of neutron pair-distribution functions allowed the difference in local atomic organization for these two ...
A new �on the fly� method to perform Born-Oppenheimer ab initio molecular dynamics (AIMD) simulations is presented. Inspired by Ehrenfest dynamics in time-dependent density functional theory, the electronic orbitals are evolved by a Schr�dinger-like equation, where the orbital time derivative is multiplied by ...
We used a variational approach adapted to a quantum molecular-dynamics code to determine the best reference potential for warm dense aluminum. This ab initio variational approach was based on the Gibbs-Bogolyubov inequality. We used many-body reference systems interacting through inverse-power-law potentials, among which the Coulomb ...
Large-scale ab initio molecular dynamics simulations of ion-solid interactions in SiC reveal that significant charge transfer occurs between atoms, and defects can enhance charge transfer to surrounding atoms. The results demonstrate that charge transfer to and from recoiling atoms can alter the energy barriers and ...
The structural environment of Mg in a K-bearing silicate glass of composition K2MgSi3O8 is investigated by x-ray absorption near-edge structure (XANES) spectroscopy at the Mg K-edge. XANES calculations are performed using a plane-wave electronic structure code, and a structural model obtained by classical molecular dynamics coupled to ...
The structural environment of Mg in a K-bearing silicate glass of composition K(2)MgSi(3)O(8) is investigated by x-ray absorption near-edge structure (XANES) spectroscopy at the Mg K-edge. XANES calculations are performed using a plane-wave electronic structure code, and a structural model obtained by classical molecular dynamics coupled to ...
Collision processes between a single gold atom and a gold cluster are investigated by means of ab initio techniques. The targets we consider are minimum energy 13 gold atom clusters. The kinetic energy of the projectile and its impact parameter are chosen within a range such that the three regimes we are mainly interested in studying (fusion, scattering ...
The atomic and electronic structure of uniformly and nonuniformly mixed Au-Co nanowires have been studied using the ab initio molecular dynamics method. The effect of elastic stretching/contraction deformations on the stability and electronic properties of mixed Au-Co nanowires has been studied. It is established ...
The pressure dependence of the static and dynamic properties of liquid boron oxide, B2O3 , is studied by ab initio molecular dynamics simulations. Planar BO3 units are found to be scarcely deformed under pressures up to about 3 GPa. Under further compression, the number of tetrahedral BO4 units increases ...
The structural and electronic properties of molten CuI are studied by means of ab initio molecular-dynamics simulations. From the first-peak positions of the partial pair distribution functions, we confirm that the nearest-neighbor distance for Cu-Cu pair is almost the same as that for Cu-I pair in spite of the correlation between the ...
We report here a direct ab initio molecular dynamics study of the p-/o-H2+HOC+ reaction on the basis of the accurate SAC-MP2 potential energy surface. The quasi-classical trajectory method was employed. This work largely focuses on the study of reaction mechanisms. A roaming mechanism was identified for this ...
The static and dynamic properties of liquid Sn at two di?erent thermodynamic states have been studied from the Orbital Free Ab-Initio Molecular Dynamics (OFAIMD) simulation method. This method is based on the density functional theory (DFT) of Hohenberg and Kohn. The exchange and correlation interaction is described here with the local ...
An ab-initio molecular dynamics procedure without precalculation of the Born-Oppenheimer energy surface based on an iterative non-local density functional method employing Gaussian atomic basis has been developed. Analytical gradients are calculated and used for the propagation of nuclei. Sufficiently long trajectories can be ...
A direct calculation of the coherent x-ray scattering spectrum of liquid water under ambient conditions is presented using ab initio density functional theory. The experimental data are compared with the calculated x-ray scattering spectra retrieved from the trajectories of two Car-Parrinello molecular dynamics ...
Ab initio molecular dynamics (AIMD) simulations are performed for studying the S0-->T1 excitation dynamics of psoralen compounds; namely, nonsubstituted psoralen, 5-methoxypsoralen (5-MOP), and 8-methoxypsoralen (8-MOP). The density functional theory calculations at the B3LYP/D95V level are used for evaluating ...
The microscopic mechanism of the metallization of liquid selenium under pressure is studied by ab initio molecular dynamics simulations. From the obtained electronic properties, such as the electronic density of states and the bond-overlap population, the pressure-induced metallization is found to be completed at a ...
The hydrogen storage is still a challenge for mobile applications. The diffusion of hydrogen in solids is considered as a general model system but there is limited knowledge available for the dynamics of hydrogen in complex hydrides. In this letter, we present a systematic approach to study the hydrogen-deuterium exchange in bulk LiBH4 based on ab initio ...
Using ab initio molecular dynamics simulations, the local atomic structure and electronic properties of supercooled liquid Si (l-Si) at different temperatures from 1700 to 1100 K were studied. Our calculated coordination numbers present no obvious change in the temperature range investigated. Our results indicate ...
We performed a comprehensive study of the static, dynamic, and electronic properties of liquid Pb at T=650K , ?=0.0309�?3 by means of 216-particle ab initio molecular dynamics simulations based on a real-space implementation of pseudopotentials constructed within density-functional theory. The predicted results ...
We present results for a comprehensive study of the static, dynamic and electronic properties of liquid Pb near melting by means of 216-particle ab initio molecular dynamics simulations based on a real-space implementation of pseudopotentials constructed within density-functional theory. The predicted results and ...
The interaction of hydrogen with palladium surfaces represents a model system for the study of the adsorption and absorption at metal surfaces. Theoretical gas-surface dynamics studies have usually concentrated on the adsorption dynamics on clean surfaces. Only recently has it become possible, based on advances in electronic structure codes and improvements in computer power, to address the much ...
Proton dissociation and transfer were examined with ab initio molecular dynamics (AIMD) simulations of carbon nanotubes (CNT) functionalized with perfluorosulfonic acid (-CF(2)SO(3)H) groups with 1-3 H(2)O/SO(3)H. The CNT systems were constructed both with and without fluorine atoms covalently bound to the walls to ...
Al bombardment induced structural changes in ?-Al2O3 (R-3c) and ?-Al2O3 (Fd-3m) were studied using ab initio molecular dynamics. Diffusion and irradiation damage occur for both polymorphs in the kinetic energy range from 3.5 to 40 eV. However, for ?-Al2O3(001) subplantation of impinging Al causes significantly ...
We describe the construction of a multi-phase equation of state for carbon at extreme pressures based on ab initio electronic structure calculations of two solid phases (diamond and BC8) and the liquid. Solid-phase free energies are built from knowledge of the cold curves and phonon calculations, together with direct ab ...
Time-reversible ab initio molecular dynamics based on a lossless multichannel decomposition for the integration of the electronic degrees of freedom [Phys. Rev. Lett. 97, 123001 (2006)] is explored. The authors present a lossless time-reversible density matrix molecular ...
Higher order factorization schemes are developed for path integral molecular dynamics in order to improve the convergence of estimators for physical observables as a function of the Trotter number. The methods are based on the Takahashi-Imada and Susuki decompositions of the Boltzmann operator. The methods introduced improve the averages of the estimators ...
Ab initio molecular dynamics calculations are adapted to treat dense plasmas for temperatures exceeding the electronic Fermi temperature. Extended electronic states are obtained in a plane wave basis by using pseudopotentials for the ion cores in the local density approximation to density functional theory. The ...
The reconstruction process of vacancy hole in carbon nanotube is investigated by tight-binding molecular dynamics simulations and by ab initio total energy calculations. In the molecular dynamics simulation, a vacancy hole is found to reconstruct into two separated ...
The equation of state (EOS) of the solar interior is accurately and smoothly determined from ab initio simulations named quantum Langevin molecular dynamics in the pressure range of 58 Mbar {<=}P {<=} 4.6 x 10{sup 5} Mbar at the temperature range of 1 eV {<=}T {<=} 1500 eV. The central ...
The stability of the zinc-blende structured MgS is studied using a constant pressure ab initio molecular dynamics technique. A phase transition into a rocksalt structure is observed through the simulation. The zinc-blende to rocksalt phase transformation proceeds via two rhombohedral intermediate phases within R3m ...
The interactions between neutral self-interstitials in silicon are studied using ab initio tight-binding molecular-dynamics simulations in periodic supercells containing 64 up to 216 Si atoms. A number of configurations with three or more self-interstitials are found, and the lowest-energy ones are discussed. The binding energies of In ...
The extended Lagrangian formulation of time-reversible Born-Oppenheimer molecular dynamics (TR-BOMD) enables the use of geometric integrators in the propagation of both the nuclear and the electronic degrees of freedom on the Born-Oppenheimer potential energy surface. Different symplectic integrators up to the 6th order have been adapted and optimized to ...
Properties of neat liquid formamide (HCONH2) have been studied by the combination of gradient-corrected density-functional theory, norm-conserving pseudopotentials, and the adaptive finite-element method. The structural and dynamical quantities have been calculated through molecular dynamics simulations under the Born-Oppenheimer approximation. ...
First-principles molecular dynamics simulations are carried out to study the structures, dynamics, and electronic properties of liquid Al{sub 88}Si{sub 12} in the temperature ranging from 898 to 1298 K. The temperature dependence of static structure factors, pair correlation functions, and electronic density-of-states are investigated. The structural ...
Resolving chemical dynamics of decomposition of energetic molecules is crucial for understanding detonation initiation in energetic materials and predicting their sensitivity to shock and impact stimuli. We employ Born-Oppenheimer molecular dynamics driven by density-functional methods to identify possible decomposition pathways in nitric esters (including ...
We study the thermophysical properties of dense helium plasmas by using quantum molecular dynamics and orbital-free molecular dynamics simulations, where densities are considered from 400 to 800g/cm3 and temperatures up to 800 eV. Results are presented for the equation of state. From the Kubo-Greenwood formula, we ...
Single-wall nanotubes can adhere to planar surfaces via van der Waals forces, and this causes the tubes to deform. We use classical molecular dynamics to estimate this deformation and density functional theory to quantify its impact on electronic band structure. For (n,0) tubes, adhesion causes the maximum bandgap to rise more rapidly with diameter, but ...
In this work we show how the ab initio determination of van der Waals coefficients within time-dependent density functional theory can be used to build efficient and accurate atomistic models that describe the long-range interactions of proteins with other proteins and of proteins with semi-conducting surfaces. The model parameters are fitted so that they ...
The dimerization of formamide (FMA) has been investigated by matrix isolation spectroscopy, static ab initio calculations, and ab initio molecular dynamics (AIMD) simulations. Comparison of the experimental matrix IR spectra with the ab ...
We have performed extensive ab initio and classical MD simulations of benzene in water in order to examine the unique solvation structures that are formed. Qualitative differences between classical and ab initio MD simulations are found and the importance of various technical simulation parameters is examined. Our ...
An ab initio study based on local-density-functional (LDF) theory is presented for the chemisorption of hydrogen on the Pd(111) surface. Our calculation uses the Vienna ab initio molecular-dynamics program (VAMP) based on (i) finite-temperature LDF, (ii) exact calculation of the electronic ...
We have calculated the melting temperature of tungsten by two ab initio approaches. The first approach can be divided into two steps. In the first step, we simulate a large coexisting solid and liquid system by the classical embedded-atom method potential and obtain an approximate melting temperature. In the second step, we compute the accurate melting ...
We have simulated exchange of inner-sphere and bulk water molecules for different sizes of Al3+(aq) clusters, Al(H2O)63+ + nH2O for n = 0, 1, 6, or 12, with ab initio and molecular dynamics simulations, in order to understand how robust the ab initio method is for ...
The structure of molten AgCl, AgI, and their eutectic mixture Ag(Cl(0.43)I(0.57)) is studied by means of molecular dynamics simulations of polarizable ion model potentials. The corresponding static coherent structure factors reproduce quite well the available neutron scattering data. The qualitative behavior of the simulated partial structure factors and ...
The structure of molten AgCl, AgI, and their eutectic mixture Ag(Cl0.43I0.57) is studied by means of molecular dynamics simulations of polarizable ion model potentials. The corresponding static coherent structure factors reproduce quite well the available neutron scattering data. The qualitative behavior of the simulated partial structure factors and ...
Studies of ring-saturated pyrimidine base lesions are used to illustrate an integrated modeling approach that combines quantum-chemical calculations with molecular dynamics simulation. Electronic-structure calculations on the lesions in Isolation reveal strong conformational preferences due to interactions between equatorial substituents to the pyrimidine ...
molecules Test Case2: 64 atom Si The CPMD code is a plane wave/pseudopotential implementation of Density IBM eServer OpenPower CPMD Version 3.9.2 The CPMD code is a plane wave/pseudopotential implementation Functional Theory, particularly designed for ab-initio molecular dynamics. CPMD Version 3.9.2 Life Sciences
The predicted superionic phase of water is investigated via ab initio molecular dynamics at densities of 2.0-3.0 g/cc (34-115 GPa) along the 2000 K isotherm. They find that extremely rapid (superionic) diffusion of protons occurs in a fluid phase at press...
The predicted superionic phase of water is investigated via ab initio molecular dynamics at densities of 2.0-3.0 g/cc (34 -115 GPa) along the 2000K isotherm.We find that extremely rapid (superionic) diffusion of protons occurs in a fluid phase at pressure...
In this paper, we generate a-Ge2Sb2Te5 models via ab initio molecular dynamic simulations, track the dynamic changes of network at 500 K, and correlate the structural changes in the course of the simulation with changes in electronic structure. Considerable fluctuations of the electronic gap are observed even for a ...
, L809. (12) Marx, D.; Hutter, J. Ab initio molecular dynamics: Theory and implementation; Modern consisting of 103-104 atoms. We find that the shape change is accompanied by a structural change as the experimental rods but much smaller sizes of about 103-104 atoms. Our results indicate that gold nanorods melt
We introduce a simple local atomic structure optimization algorithm which is significantly faster than standard implementations of the conjugate gradient method and often competitive with more sophisticated quasi-Newton schemes typically used in ab initio calculations. It is based on conventional molecular dynamics ...
The structural stability of protonated methane \\(CH +5\\) and acetylene \\(C2H +3\\) has been investigated with ab initio molecular dynamics. In CH +5, the hydrogen atoms execute large amplitude pseudorotational motions. The hydrogen migrations are not disturbed by complexation with a hydrogen molecule. In ...
Here we demonstrate and characterize the H-diffusion behavior around a screw dislocation in body-centered cubic (bcc) ?-Fe by performing path-integral molecular dynamics modeling and adopting an ab initio�based potential. Counterintuitively, our results indicate that the H diffusivity along the dislocation line ...
A SERS investigation combined with ab initio computational analysis involving Car-Parrinello molecular dynamics simulations and Density Functional Theory approach allows fundamental information to be obtained on the behaviour of thiazole in silver aqueous suspension where solvation and chemisorption processes ...
in Molecular Wires Alexander B. Pacheco and Srinivasan S. Iyengar Department of Chemistry, Indiana University through molecular wires. The simultaneous dynamics of electrons and nuclei in the wire is coupled are common tools for studying such system. � The system consists of a molecular wire system sandwiched
Using constant-pressure ab initio molecular dynamics we have simulated the conversion of carbon from graphite to diamond under high pressure. We found that the transformation path proceeds through sliding of graphite planes into an unusual orthorhombic stacking, from which an abrupt collapse and buckling of the ...
The dynamics of the ethylene molecule in femtosecond laser pulses is studied as a function of the laser parameters using an ab initio time-dependent approach, called nonadiabatic quantum molecular dynamics. We predict that, by choosing different femtosecond pulses with well-defined excitation frequencies, one can ...
Nano-plasticity of thin single-wall carbon nanotubes under uniaxial compression is investigated through generalized tight-binding molecular dynamics (GTBMD) and ab-initio electronic structure methods. A novel mechanism of nano-plasticity of carbon nanotub...
Melting and multipole deformations of sodium clusters with up to 55 atoms are studied using an ab initio molecular dynamics method. The melting temperature regions for Na20, Na40, and Na55+ are estimated. The melting temperature region determined here for Na55+ agrees with the one determined experimentally. The ...
The profiles of the potential of mean force for the Cl- - H3O+ pair, as predicted by two ab initio models, are determined by constraint molecular dynamics simulation at a near-critical condition. The corresponding association constants are then ...
Ab initio molecular dynamics calculations have shown that the lxl:2H and the 2xl:H surfaces of diamond(C)(100) have a (-) electron affinity(EA); the clean (100) surface has a (+) EA. This is in agreement with experiment. Biased nucleation of C on Beta-SiC...
Hydrogen is considered a promising candidate to achieve an alternative source to overcome future energy supply problems. Very recently, an ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides appeared by Ramzan and Ahuja [J. Appl. Phys. 106, 016104 (2009)]. Here, we ...
The formation of As and Se atom-incorporated fullerenes has been investigated by using radionuclides produced by nuclear reactions. From the trace of radioactivities of 72As, and 75Se after High Pressure Liquid Chromatography (HPLC), it was found that the formation of endohedral fullerenes or heterofullerenes is possible by a recoil process following the nuclear reactions. To confirm the produced ...
We have investigated the influence of a variety of dimer vacancy defects on the reactivity of F2 molecules with the clean Si(100)-2 x 1 reconstructed surface via molecular dynamics using an ab-initio-derived Stillinger-Weber-type many-body potential. Our ...
�Oppenheimer approximation. QMC methods for hydrogen do not rely on pseudopotential approximations and treat electron performed using the Born� Oppenheimer molecular dynamics method, with the CPMD simulation pack- age (49 conserving nonlocal pseudopotential with a core radius of rc � 0.5 a:u. to represent hydrogen. The equations
to the Grotthus mechanism observed in water25-29 and other hydrogen-bonded liquids such as methanol30 and hydrogen has been used before to study hydrogen bond kinetics in liquid water.56,57 Though the short time water (and in other hydrogen-bonded liquids), excess protons move in a similar way and this mode
In order to find the equilibrium geometries of molecules and solids and to perform ab initio molecular dynamics, it is necessary to calculate the forces on the nuclei. We present a correlated sampling method to efficiently calculate numerical forces and potential energy surfaces in diffusion Monte Carlo. This ...
deposition on Al(111) - STM FOV: 23 nm. Ti/Al(111) deposited at 400 K. #12;10 FT-IR Spectroscopy - atomic H, time-resolved, high-pressure. � X-ray microprobe � IR micro-spectroscopy � Surface microscopy & energetics. Ab-initio molecular dynamics - surface dynamics. FT-infrared reflection spectroscopy - hydrogen
The stiffness and plasticity of boron nitride nanotubes are investigated using generalized tight-binding molecular dynamics and ab-initio total energy methods. Due to boron-nitride BN bond buckling effects, compressed zigzag BN nanotubes are found to unde...
We study the potential energy landscape underlying the motion of monatomic liquids by quenching from random initial configurations (stochastic configurations) to the nearest local minimum of the potential energy. We show that this procedure reveals the underlying potential energy surface directly. This is in contrast to the common technique of quenching from a molecular ...
First-principles molecular dynamics simulations were used to calculate the sound velocity of dense hydrogen, and the results were compared with extrapolations of experimental data that currently conflict with either astrophysical models or data obtained from recent global oscillation measurements of Jupiter. Excellent agreement with the extrapolated ...
The atomic and electronic structures of Ge dimers adsorbed on top of a Si(100) flat surface has been investigated by first-principles molecular dynamics method. Four high-symmetry configurations have been considered and thoroughly relaxed. The most stable configuration for Ge dimers is found to be on the trough, in the middle of, and parallel to the ...
We calculate the static structure factor of dense multi-component plasmas. Large scale ab initio finite-temperature DFT molecular dynamics simulations are performed in order to cover the region where a consistent quantum treatment for the electrons is inevitable. Especially, the behavior at small wave numbers k can ...
The importance of quantum effects as well as the accuracy of the ab initio-based polarizable TTM2.1-F force field in describing liquid water are quantitatively assessed by a detailed analysis of the temperature dependence of several thermodynamic and dynamical properties computed using the path-integral molecular ...
The magma ocean process in the early history of the Earth has a great influence on the light element identities and contents of the core which subsequently affect the energy of the geodynamo provided by the compositional convection and the inner core growth through their effect on the phase diagram of iron alloy. In the present work, a two-phase ab-initio ...
Structures of the ground state pyrrole-(H2O)n clusters are investigated using ab initio calculations. The charge-transfer driven femtosecond scale dynamics are studied with excited state ab initio molecular dynamics simulations employing the complete-active-space ...
Incoherent inelastic neutron scattering is used to probe the effects of dihydrogen bonding on the vibrational dynamics in the molecular crystal of ammonia borane. The thermal neutron energy loss spectra of (11)B enriched ammonia borane isotopomers ((11)BH(3)NH(3), (11)BD(3)NH(3), and (11)BH(3)ND(3)) are presented and compared to the vibrational power spectrum calculated using ...
We report the e?ects of system size on melting of dense sodium at about 100 GPa. We have performed systematic ab initio molecular-dynamics (MD) simulations with the number of atoms at most 250 for bcc and 256 for fcc structures based on 3s-valence-electron model and 2p3s-valence-electron model. We have shown that the inner-core 2p ...
The structure dependent magnetism and intermixing characteristics of Ti/Fe(001) thin films were investigated using molecular dynamics simulations and ab initio calculations. Through density functional theory based ab initio calculations, sharply decreased demagnetization ...
We have studied the liquid surface of sodium with extensive ab initio molecular dynamics simulations based on ensemble density-functional theory. We find clear evidence of layering in the direction perpendicular to the surface that persists to temperatures more than 100 K above the melting point. We also observe ...
A molecular dynamics (MD) study of the static and dynamic properties of molten and glassy germanium dioxide is presented. The interactions between the atoms are modeled by the classical pair potential proposed by Oeffner and Elliott (OE) (1998 Phys. Rev. B 58 14791). We compare our results to experiments and previous simulations. In addition, an ...
Lithium-ion batteries have the potential to revolutionize the transportation industry, as they did for wireless communication. A judicious choice of the liquid electrolytes used in these systems is required to achieve a good balance among high-energy storage, long cycle life and stability, and fast charging. Ethylene-carbonate (EC) and propylene-carbonate (PC) are popular electrolytes. However, to ...
On-the-fly, ab initio classical molecular dynamics are demonstrated with an underlying dual basis set potential energy surface. Dual-basis self-consistent field (Hartree-Fock and density functional theory) and resolution-of-the-identity second-order M�ller-Plesset perturbation theory (RI-MP2) dynamics are tested ...
