... This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and ...
DTIC Science & Technology
... nightmares for traditional quantum chemical approaches for optimizing structures of such ... an unbiased manner with ab initio forces. ...
... from federally funded research, testing and training ... agencies for Research Development Test and Evaluation ... Title : AB Initio Propagator Theory of ...
Metal atom clusters are studied based on the application of ab initio quantum mechanical approaches.
NASA Technical Reports Server (NTRS)
A global search for possible LiF cluster structures is performed up to (LiF)(8). The method is based on simulated annealing, where all the energies are evaluated on the ab initio level. In addition, the threshold algorithm is employed to determine the energy barriers for the transitions among these structures, for the ...
PubMed
... cluster. The temperature-corrected formation enthalpy of the cluster is -8.7 kcal/mol relative to three isolated HCN molecules. ...
Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Car...
National Technical Information Service (NTIS)
The adsorption energies of methane and ethane in zeolites are investigated with ab initio molecular orbital theory and density functional theory. In this work we have used zeolite cluster models containing two, three, and five tetrahedral (Si, Al) atoms a...
General procedures for computing alloy phase equilibria from ab initio electronic structure calculations are reviewed and applied to the Al-Li phase diagram. Free energies were calculated by the cluster variation method (CVM) in the tetrahedron approximat...
This study involves: Ab-initio crystal orbitals and polymer orbitals; Ab-initio coupled cluster program; Ab-initio quantum chemical calculations and electrostatic molecular potential contour maps for cationic polymerization; Prediction of crystal density;...
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 agreement. The properties of hydrogen bonded clusters (water ...
NASA Astrophysics Data System (ADS)
Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Li(n)(-), n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found ...
Structural and energetic properties of small, deceptively simple anionic clusters of lithium, Lin-, n = 3-7, were determined using a combination of anion photoelectron spectroscopy and ab initio calculations. The most stable isomers of each of these anions, the ones most likely to contribute to the photoelectron spectra, were found ...
... including superlattice, nanoparticles, and piezoelectric oxide supported metal. To perform this research, we will use ab-initio density functional ...
The CCSD(T) method, singles and doubles coupled-cluster theory plus a perturbational estimate of the
Molecular orbital calculations on the nickel pentamer cluster were carried out using ab initio methods as well as density functional methods. The molecular orbital cluster approach using effective core potentials (ECP) was used for the ab initio calculati...
The molecular cluster model approach for the description of processes at surface is presented. It involves using finite clusters which contain surface atoms interacting with atomic or molecular adsorbates. Accurate ab initio wavefunctions can be obtained ...
An approach is developed to enhance sampling for ab initio Monte Carlo and ab initio path integral Monte Carlo calculations of molecular clusters by utilizing an approximate potential as a guide to move in the configuration space more efficiently. The interpolated potential energy obtained by ...
Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Carlo sampling of nuclear configurations. ...
Energy Citations Database
We have calculated molecular geometries and electric polarizabilities for small cadmium selenide clusters. Our calculations were performed with conventional ab initio and density functional theory methods and Gaussian-type basis sets especially designed for (CdSe)(n). We find that the dipole polarizability per atom converges rapidly to ...
There has been an interest in the study of hydrogen ion clusters. However, only positive clusters, Hn +, where n = 3m 5, 7, ..., have been discovered and successfully analyzed by meand of both experimental and ab initio theoretical methods (cf. Hirao and ...
Although C sub 3+ is considered to be the fundamental building block of the larger carbon clusters, the geometry of this molecule is unknown. Several authors have reported results of ab initio calculations in which the optimized geometry of the ion is ded...
Metal atom clusters are studied based on the application of ab initio quantum mechanical approaches. Because these large 'molecular' systems pose special practical computational problems in the application of the quantum mechanical methods, there is a spe...
The application of ab initio quantum mechanical approaches in the study of metal atom clusters requires simplifying techniques that do not compromise the reliability of the calculations. Various aspects of the implementation of the effective core potentia...
The structure and energetics of free radicals, ions, and clusters have been investigated by photoelectron photoion coincidence (PEPICO) and analyzed with the aid of ab initio molecular orbital and statistical theory (RRKM) calculations. The two major them...
The structure and energetics of free radicals, ions, and clusters have been investigated by photoelectron photoion coincidence (PEPICO) and analyzed with ab initio molecular orbital and statistical theory RRKM calculations. In these experiments, molecules...
Ab initio calculations of the electronic structure of Hn- and Hn+ clusters have been carried out using accurate Gaussian basis sets and with levels of theory up to fourth-order perturbation theory (MP4) and single and double excitation configuration inter...
Ab-initio quantum chemical computations have been applied to a set of molecular clusters derived from Si5H12 to model defects in crystalline silicon involving boron, carbon, nitrogen, oxygen, and hydrogen. In computations of defect structure, hydrogen ato...
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...
The reaction of C(3P) with H2S to HCS/HSC isomers is investigated with high level ab initio methods. Besides reaction energies to form HCS/HSC, the energetics and properties of different singlet/triplet H2CS reaction intermediates are studied. The combination of ab initio theory and crossed molecular beams ...
A systematic method for approximating the ab initio electronic energy of crystal lattices has been improved by the incorporation of long range electrostatic and dispersion interactions. The effect of these long range interactions on the optimization of the crystal structure is reported. The harmonic lattice dynamics have been evaluated to give phonon ...
The rotational mechanism of the NH{sub 4}{sup +} ion in water is analyzed by using both semiempirical (AM1) and ab initio (6-31G* SCF level) methods. AM1 predicts rapid rotation at any degree of first solvent shell hydration from n = 1-6. These results are considered artifactual since AM1 favors ion-water structures of a type not found in ...
The GaAs(100) surface is modeled by using atomic clusters in order to study the effects of passivation with sulfur. Both the Ga- and the As-terminated surfaces are tied off with S atoms in a 2 {times} 1 reconstruction. The most stable structure is established on the basis of ab initio Hartree-Fock calculations. It is found that after ...
Results of ab initio Hartree-Fock calculations are presented for the nine-coordination-shell cluster Be{sub 69}. Binding energy, ionization potential, electrical field gradient, nuclear-electrostatic potential, diamagnetic shielding constant, second moments of charge, and Mulliken populations are reported for several electronic states. ...
We perform coupled-cluster and diffusion Monte Carlo calculations of the energies of circular quantum dots up to 20 electrons. The coupled-cluster calculations include triples corrections and a renormalized Coulomb interaction defined for a given number of low-lying oscillator shells. Using such a renormalized Coulomb interaction brings the ...
It is essential to know the arrangement of the atoms in a material in order to compute and understand its properties. Searching for stable structures of materials using first-principles electronic structure methods, such as density-functional-theory (DFT), is a rapidly growing field. Here we describe our simple, elegant and powerful approach to searching for structures with DFT, which we call ...
Dissociation and fission of small neutral, singly and doubly charged strontium clusters are studied by means of ab initio density functional theory methods and high-resolution time-of-flight mass spectrometry. Magic numbers for small strontium clusters possessing enhanced stability towards monomer evaporation and ...
E-print Network
We have employed ab initio molecular dynamics to investigate the equilibrium geometries, energetics, and the nature of bonding in mixed Li-Sn clusters. Our studies reveal that a small percentage of Sn in Li-rich clusters introduces significant changes in the equilibrium geometries. It is also seen that the ...
Recent experimental work by Strobel et al. [T.A. Strobel, M. Somayazulu, R.J. Hemley, Phys. Rev. Lett. 103 (2009) 065701] on a molecular solid subjected to high pressures has motivated the present study. We first investigate a molecular cluster containing one silane molecule plus two H2 molecules, by ab initio quantum mechanics. ...
... al.18] who use Muliken ab initio STO-3G atomic net charges to suggest that in ferrierite zeolite there is a + 1.5 charge on the ... zeolite sample ...
A theoretical research investigation of materials that are potential additives for solid hydrogen rocket fuels is investigated. The ab initio calculations show that mixed clusters of boron and lithium prefer to have an electronegative boron atom at the mi...
The structure of atomic clusters is investigated using methods of ab initio quantum chemistry in conjunction with scanning tunneling microscopy (STM). Gold sols are imaged via STM and their sizes characterized. Atomic resolution reveals facets, steps, and...
Very efficient computer codes to perform many-body perturbation theory (MBPT) and coupled cluster method (CCM) calculations have been written and employed for the first time in large-scale ab initio calculations of potential energy surfaces.
Very efficient computer codes to perform many-body perturbation theory (MBPT) and coupled cluster method (CCM) calculations have been written and employed for the first time in large-scale ab initio calculations of potential energy surfaces. (Author)
Under AFOSR support over several years, coupled-cluster (CC) and many-body perturbation theory (MBPT) methods for the accurate inclusion of electron correlation in ab initio quantum chemical calculations of molecules have been definitively established as ...
The catalytic properties of cobalt oxide (Co0) were investigated theoretically. The interactions of atomic hydrogen with small clusters of atoms, representing cobalt oxide surfaces, were calculated using the ab initio Unrestricted Hartree-Fock (UHF) metho...
The nature of the bonding between halogen atoms (F, CI and Br) and the Ag (111) surface has been investigated by analyzing ab initio Hartree- Fock wave functions for cluster models of the Ag surface and a halogen atom. Using a variety of criteria, we conc...
ACES II, a new program system for ab initio electronic structure calculations is described. The strengths of ACES II involve the use of many-body perturbation theory (MBPT) and coupled-cluster (CC) theory for calculating the energy, geometry, spectra, and...
- oms and oxygen atoms in clusters, one could observe the metallic to ionic transition. Studies. In the stoichiometric cluster of Ba8O8 , the binding is completely ionic, the HOMO is essen- tially the 2p orbits a significant energy gaps in the range of 0.7�1.2 eV. Finally, in SC cluster, the bonding is fully ionic
In this paper we examine the properties of small cluster models of La(sub 2)CuO(sub 4). In Section 2, the Madelung/Pauli background potential used to imbed the primary cluster and the basis sets used to expand the cluster wavefunction are discussed. Secti...
... Title : Chalcopyrite Magnetic Semiconductors: An Ab-Initio Study of Their Structural, Electronic and Magnetic Properties. ...
... from federally funded research, testing and training ... for Research Development Test and Evaluation ... COMPENDIUM OF AB INITIO CALCULATIONS ...
... Accession Number : ADA219907. Title : An Ab Initio Study of the Geometry and Rotational Barrier of 4- Phenylimidazole. ...
... from federally funded research, testing and training ... and agencies for Research Development Test and Evaluation ... Title : Ab Initio Calculations of the ...
... Title : Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields. ...
... Title : AB Initio Quantum Chemical Investigations of Solubilities in Supercritical Solutions. Descriptive Note : Conference Paper,. ...
Certain classes of temperature-composition binary alloy phase diagrams can now be computed in an ab-initio'' approach. No adjustable or experimentally fitted parameter is used. The expectation value of the energy is expressed in terms of an expansion of cluster probabilities, where the prefactors, the Effective ...
Certain classes of temperature-composition binary alloy phase diagrams can now be computed in an ``ab-initio`` approach. No adjustable or experimentally fitted parameter is used. The expectation value of the energy is expressed in terms of an expansion of cluster probabilities, where the prefactors, the Effective Cluster Interaction, ...
: Access to high-performance computing power remains crucial for many computational chemistry problems. Unfortunately, traditional supercomputers or cluster computing solutions from commercial vendors remain very expensive, even for entry level configurations, and are therefore often beyond the reach of many small to medium-sized research groups and universities. ...
Phenol-ammonia clusters with more than five ammonia molecules are proton transferred species in the ground state. In the present work, the excited states of these zwitterionic clusters have been studied experimentally with two-color pump probe methods on the nanosecond time scale and by ab initio ...
To explore the possible existence of boron clusters without carbon analogs, we study B(84) cluster as a prototypical system by ab initio calculations. Structures of several isomer forms of B(84) are optimized. Among these isomers, a group of amorphous (disordered) structures are found to be the most stable. ...
... Title : AB Initio Study of the Electronic Magnetic Circular Dichroism ... functions are determined using as initio quantum chemical techniques including ...
To ab initio simulate an ionic crystal using a cluster of atoms, one must surround that cluster with point charges. These point charges add the effect of the electrostatic potential of the rest of the crystal on the electronic structure of the quantum cluster. The value of the point charges has ...
The framework of ab initio density-functional theory (DFT) has been introduced as a way to provide a seamless connection between the Kohn-Sham (KS) formulation of DFT and wave-function based ab initio approaches [R. J. Bartlett, I. Grabowski, S. Hirata, and S. Ivanov, J. Chem. Phys. 122, 034104 (2005)]. Recently, ...
Due to recent advances in methods and computers, the accuracy of ab calculations has reached a point
The ab initio/classical free energy perturbation (ABC-FEP) method proposed previously by Wood et al. [J. Chem. Phys. 110, 1329 (1999)] uses classical simulations to calculate solvation free energies within an empirical potential model, then applies free energy perturbation theory to determine the effect of changing the empirical solute-solvent interactions ...
We describe a method for calculating thermodynamic properties of ionic liquids by using standard quantum statistical thermodynamics as characterized by ab initio techniques. We review briefly how thermochemical properties for different sized clusters of ionic liquids are calculated by standard ab ...
We revive intriguing, yet still unexplained, experimental results of Ehrlich and co-workers [Phys. Rev. Lett. 77, 1334 (1996)10.1103/PhysRevLett.77.1334; Phys. Rev. Lett. 67, 2509 (1991)10.1103/PhysRevLett.67.2509] who have observed, that 5d adatoms distributed on (111) surface islands of 5d metals favor the adsorption at the cluster�s edge rather than at the ...
Quantum-mechanical molecular dynamics have been used to investigate structural and physical properties of the 1/1 approximant of the icosahedral Al-Cu-Fe quasicrystal. Particular local structural arrangements of atoms, referred to here as clusters, have been analyzed with respect to their properties within the crystal structure. Artificial strain and cracks have been ...
Atomic geometries, electronic structures, and magnetic moments of several metal clusters with 13 atoms are studied by ab initio density-functional calculations. The ground state structures of 13-atom metal clusters were previously assumed to be icosahedron, cuboctahedron, or decahedron. However, in this study, ...
We develop a new ab initio many-body approach capable of describing simultaneously both bound and scattering states in light nuclei, by combining the resonating-group method with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters. This approach preserves translational symmetry and ...
We present full-dimensional potential energy surfaces (PESs) for hydrated chloride based on the sum of ab initio (H(2)O)Cl(-), (H(2)O)(2), and (H(2)O)(3) potentials. The PESs are shown to predict minima and corresponding harmonic frequencies accurately on the basis of comparisons with previous and new ab initio ...
Raman spectra of thin solid electrolyte films obtained by sputtering a Li2SO4 target in nitrogen plasma are measured and compared to ab initio electronic structure calculations for clusters composed of 28 atoms. Agreement between measured and calculated spectra is obtained only when some oxygen atoms are replaced by nitrogen atoms and ...
To assist the proposed search for the electric dipole moment of the electron with the thorium oxide, converged ab initio coupled cluster calculations are performed on the interaction energy, dipole moment, anisotropic static dipole polarizability, and quadrupole moment of the ThO(X 1?+) molecule as functions of internuclear distance. ...
To assist the proposed search for the electric dipole moment of the electron with the thorium oxide, converged ab initio coupled cluster calculations are performed on the interaction energy, dipole moment, anisotropic static dipole polarizability, and quadrupole moment of the ThO(X (1)Sigma(+)) molecule as functions of internuclear ...
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 identifying hydrolytic ...
A new ab initio potential energy surface of the Ne�CO complex is developed using single and double excitation coupled-cluster theory with noniterative treatment of triple excitations [CCSD(T)]. The potential has a minimum value of ?49.396 cm?1 at Re = 6.40a0 with approximately T-shaped geometry (?e = 82.5�). Bound state energies ...
High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic electron affinities of the five canonical DNA and RNA nucleobases: uracil, thymine, cytosine, adenine, and guanine. The present results aim for the accurate determination of the ...
General procedures for computing alloy phase equilibria from ab initio electronic structure calculations are reviewed and applied to the Al-Li phase diagram. Free energies were calculated by the cluster variation method (CVM) in the tetrahedron approximation for the fcc and bcc lattices and ordered superstructures. Input was provided ...
The stability of He in hcp-Ti was studied using ab initio method based on density functional theory. The results indicate that a single He atom prefers to occupy the tetrahedral site rather than the octahedral site. The interaction of He defects with Ti atoms has been used to explain the relative stabilities of He point defects in hcp-Ti. The relative ...
Nano-sized clusters of various materials are recent experimental targets, since they exhibit size-dependent physico-chemical properties. A vast amount of literature is available on the study of molecular clusters but general methods for systematic evolution of their growth are rather scarce. The present work reports a molecular cluster ...
Ab initio calculations using SCF approach for and analysis of results of investigation of the electronic structure of the clusters RAn+:[L]k with rare earths or actinides were carried out for the clusters in solids and liquids. Theoretical results for the electronic structure, radial integrals and energy of X- ray ...
The process of electron localization on a cluster of 32�water molecules at 20, 50, and 300�K is unraveled using ab�initio molecular dynamics simulations. In warm, liquid clusters, the excess electron relaxes from an initial diffuse and weakly bound structure to an equilibrated, strongly bound species within 1.5�ps. In contrast, ...
Tunable VUV laser was used to initiate the ion-molecule reactions in the clusters of ethanol and 1-propanol by photoionization in the region between 10.49 to 10.08 eV. Ionic products were detected by the time-of-flight mass spectrometer. In addition to the protonated clusters from proton transfer reactions, the products corresponding to ? carbon-carbon ...
Novel carbon nanotube-metal cluster structures are proposed as prototype systems for molecular recognition at the nanoscale. Ab initio calculations show that already the bare nanotube cluster system displays some specificity because the adsorption of ammonia on a carbon nanotube-Al cluster ...
We present ab initio calculations of the magnetic moments and magnetic anisotropy energies of small FeCo clusters of varying composition on top of a Cu(100) substrate. Three different cluster layouts have been considered, namely, 2 x 2, 3 x 3, and crosslike pentamer clusters. The ratio of Co ...
The structure of atomic clusters is investigated using methods of ab initio quantum chemistry in conjunction with scanning tunneling microscopy (STM). Gold sols are imaged via STM and their sizes characterized. Atomic resolution reveals facets, steps, and reconstructed surfaces of the sols. STM images of graphite surfaces are ...
We report ab initio calculations of the electronic and magnetic properties of small Co clusters. We performed pseudopotential-based and all-electron calculations. In view of the ``unwritten theorem'' that electron localization enhances the electronic correlations, we have also considered the LDA+U functional, which is tailored for the ...
We employ recent flexible ab initio potential energy and dipole surfaces [Y. Wang, X. Huang, B. C. Shepler, B. J. Braams, and J. M. Bowman, J. Chem. Phys. 134, 094509 (2011)] to the calculation of IR spectra of the intramolecular modes of water clusters. We use a quantum approach that begins with a partitioned normal-mode analysis of ...
In contrast with the single atom, atomic van der Waals clusters can form stable anions where the excess electron is bound due to long-range correlations with the electrons of the cluster. We report on extensive all-electron many-body ab initio studies on Xe clusters. Three-dimensional, planar, ...
The great power of the cluster-expansion method for atomistic simulations of the ground state properties and the thermodynamic properties of multi-component solids is highlighted. In the first part of the paper some recently developed combinations of this method with other atomistic simulation techniques (N-body potentials and cluster functionals) are ...
The ab initio atom-centered density matrix propagation (ADMP) method has been employed to study the dynamics of protonated water clusters of various sizes. An interesting result that hints at the possible amphiphilicity of the hydronium ion is detected. The hydrated proton tends to reside on the surface of the water ...
Temperature and pressure dependent decomposition kinetics of HS2O7-(H2SO4)x (x=1-3) cluster ions were measured in a quadrupole ion trap mass spectrometer. The kinetic data were analyzed with a master equation model to obtain the decomposition energies and energy transfer parameters for channels leading to elimination of sulfur trioxide and in some cases sulfuric acid. The ion ...
Using a quasi-ab initio molecular-dynamics method we have studied two-dimensional (2D) versus three-dimensional (3D) structures in Co clusters deposited on Cu(001) finding that the magnetism plays a relevant role. For the magnetic Co25 supported cluster, the influence of such a 2D to 3D structural change on the ...
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 ...
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 calculated at an acceptable computational cost, ...
Molecular orbital theory is used in the context of ab initio Hartree-Fock calculations to study the origin of quantum confinement effects in layered Pb{sub 7}I{sub 14} clusters. As the cluster geometry is energy optimized in several steps, the structure distends into two quasi-hemispherical iodine layers ...
We present an application of the bond additivity model to structural units of typical glass-forming materials with the use of ab initio molecular orbital theory. In order to estimate the refractive indices and third-order nonlinear optical susceptibilities of these materials, bond and reduced polarizabilities of the small cluster ...
We report preliminary large scale ab initio calculations of ground and excited states of {sup 16}O using quantum chemistry inspired coupled cluster methods and realistic two-body interactions. By using the renormalized Hamiltonians obtained with a no-core G-matrix approach, we obtain the virtually converged results at the level of ...
An ab initio study of gaseous clusters of O2- and O3- with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find that anionic O2-(H2O)n ...
to solid rocket propellant where it can react exothermically with the products of combustion of other fuels and kinetics of silicon hydride cluster formation during thermal decomposition of silane, J. Phys. Chem. B 103.V. Bhandarkar, M.T. Swihart, S.L. Girshick, U.R. Kortshagen, Modeling of silicon hydride clustering in a low
atom of the phenolic hydroxy group is found to decrease upon electronic excitation of the chromophore. DOI: 10.1063/1.1638378 I. INTRODUCTION van der Waals clusters between aromatic molecules and noble gas atoms have been investigated in the past in great detail. In all cases the noble gas is found
Ab initio calculations of isomeric carbon clusters C sub n(0) and C sub n(+), n = 2-4, yield structures and energies similar to previous reports, although five (not two) C4(+) structures have local energy minima. Dissociative ionization of structurally va...
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...
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 dominating deformation ...
This paper discusses basics of high performance computing on the example of the Latvian SuperCluster (LASC), installed at the Institute of Solid State Physics of the University of Latvia. The application of LASC to abinitio simulations of x-ray absorption spectra from nanoparticles is considered as a particular case. [Keywords: high performance computing, ...
Anharmonic vibrational frequencies and intensities are computed for hydrogen fluoride clusters (HF)n
Collision experiments and high-level ab initio calculations are used for the first characterization of the neutral, cationic and anionic Si3N cluster molecules. The experimentally observed fragmentation processes are well described by calculated reaction energies of all dissociation channels. In addition, the geometries and harmonic ...
The temperature and heat capacity of isolated atomic clusters are studied in terms of an ab initio statistical theory of kinetic energy distribution by atomic evaporation. Two definitions of canonical temperature are examined and numerically compared: One is based on the most probable kinetic energy release (KER), whereas the other is ...
The Ca3 and Ca4 metallic clusters have been investigated using state-of-the-art ab initio quantum mechanical methods. Large atomic natural orbital basis sets have been used in conjunction with the singles and doubles coupled-cluster (CCSD) method, a coupl...
The importance of many-body interactions is investigated for m=4,6,8 in Cu(sup 2+)(H(sub 2)O)m clusters using ab initio molecular orbital theory. A slow convergence of the interaction terms to the full many-body result is found similar to what was found i...
In sharp contrast to molecules, electronic states of clusters with an excited intermediate-shell electron can efficiently decay via an intermolecular Coulombic mechanism. Explicit examples are presented using large scale {ital ab initio} propagator calculations. The mechanism is illustrated and its generality is stressed. {copyright} ...
Ab initio, embedded-cluster RHF-SCF-LCAO molecular-orbital calculations were performed on both ground and excited states of the Tl(l) center in potassium chloride. Effective core potentials and valence orbitals were employed on the thallium atom and its n...
The potential energy surface for trimers of hydrogen fluoride is examined for multiple arrangements of the three-molecule cluster. Several established approaches to model the potential energy are examined, including a strictly pairwise additive potential, an established polarizable potential model, another, strictly three-body polarizable model, and a three-body potential ...
An ab initio approach to determining the appropriate potential in which to embed a cluster in order to simulate a larger system is proposed. For ionic and covalent systems, simple approximations are presented as obtained by systematic simplifications of the more general theory. It is also seen that for metallic systems such a reduction ...
Using ab initio molecular dynamics simulations, we find direct evidence that icosahedral clusters have a strong tendency to aggregate in Zr1?xCux liquids. Remarkably, the dynamic arrest effect is much more significant in aggregated icosahedral clusters than in nonaggregated ones by a factor of 2 or more. ...
Ab initio simulations and calculations were used to study the structures and stabilities of copper oxide clusters, Cu(n)O(n) (n = 1-8). The lowest energy structures of neutral and charged copper oxide clusters were determined using primarily the B3LYP/LANL2DZ model chemistry. For n ? 4, the ...
The pinning of size-selected AuN and NiN clusters on graphite, for N=7-100 , is investigated by means of molecular dynamics simulations and the results are compared to experiment and previous work with Ag clusters. Ab initio calculations of the binding of the metal adatom and dimers on a graphite surface are ...
... AB-INITIO SIMULATION OF a/2110> ... 4. TITLE AND SUBTITLE AB-INITIO SIMULATION OF a/2110> SCREW DISLOCATIONS γ-TiAl 5c. ...
... ADP012740 TITLE: Ab Initio Study on Spin Polarization of III-V Compound Tips ... Ab initio study on spin polarization of III-V compound tips ...
Ab initio electronic structure methods can supplement CALPHAD in two major ways for subsequent applications to stability in complex alloys. The first one is rather immediate and concerns the direct input of ab initio energetics in CALPHAD databases. The o...
...with this part. The certificate shall be void ab initio for those vehicles causing the...issued, and the certificate may be deemed void ab initio. (C) The manufacturer...with this part. The certificate shall be void ab initio for those vehicles causing...
Code of Federal Regulations, 2010
The geometric and electronic structures of Sin, Sin-, and PSin-1 clusters (2<=n<=13) have been investigated using the ab initio molecular orbital theory formalism. The hybrid exchange-correlation energy functional (B3LYP) and a standard split-valence basis set with polarization functions (6-31+G(d)) were employed to optimize ...
A metal-boron mixed cluster LiB6- was produced and characterized by photoelectron spectroscopy and ab initio calculations. A number of electronic transitions were observed and used to compare with theoretical calculations. An extensive search for the global minimum of LiB6- was carried out via an ab ...
A metal-boron mixed cluster LiB(6) (-) was produced and characterized by photoelectron spectroscopy and ab initio calculations. A number of electronic transitions were observed and used to compare with theoretical calculations. An extensive search for the global minimum of LiB(6) (-) was carried out via an ab ...
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 self-consistent-field method ...
We report full-dimensional, ab initio potential energy and dipole moment surfaces, denoted PES and DMS, respectively, for arbitrary numbers of water monomers. The PES is a sum of 1-, 2-, and 3-body potentials which can also be augmented by semiempirical long-range higher-body interactions. The 1-body potential is a spectroscopically accurate monomer ...
The equation of state (EOS) of alloys at high pressures is generalized with the cluster expansion method. It is shown that this provides a more accurate description. The low temperature EOSs of Ni-Al alloys on FCC and BCC lattices are obtained with density functional calculations, and the results are in good agreement with experiments. The merits of the generalized EOS model ...
In this paper we report a theoretical study of the static dipole polarizability of two one-dimensional structures: (a) linear carbon chains Cn (n=2-10) and (b) ladderlike planar boron chains Bn (n=4-14). The polarizabilities of these chains are calculated both at the Hartree-Fock and the correlated levels by applying accurate ab initio quantum-chemical ...
We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na(3) cluster and present the adiabatic PESs for the electronic states 2(2)E' and 1(2)A(1)', and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC ...
We perform ab initio calculation using quantum chemistry package (MOLPRO) on the excited states of Na3 cluster and present the adiabatic PESs for the electronic states 22E' and 12A1', and the non-adiabatic coupling (NAC) terms among those states. Since the ab initio calculated NAC elements for ...
A combination of ab initio and statistical thermodynamics, i.e., the cluster variation method (CVM), is applied to describe the FCC-based {gamma}-Fe[N]/{gamma}'-Fe{sub 4}N{sub 1-x} phase equilibrium. The ab initio calculated internal energies of ordered compounds, using the ...
This work is devoted to the elucidation of the applicability of the jellium model to the description of alkali cluster properties. We compare the jellium model results with those derived within ab initio theoretical approaches and with experiments. On the basis of Hartree-Fock and local-density approximations we have calculated the ...
Density-based ab initio molecular dynamics has been used to investigate the stability and ground-state geometries of heteronuclear clusters of 0953-8984/8/17/001/img2 and 0953-8984/8/17/001/img3. Our investigations of these clusters indicate that the s - p bonded electrons favour a tetrahedral coordination, which ...
An ab initio study of gaseous clusters of O2- and O2- with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find that anionic O2-(H2O)n ...
... Accession Number : ADA351780. Title : Ab Initio and DFT Potential Energy Surfaces for Cyanuric Chloride Reactions. Descriptive Note : Final rept. ...
... Ab initio study on atomic structures and physical properties of CdSe quantum nanodots ... Figure 2. Diagram of covered nanodots. ...
... Title : Ab Initio Study on Atomic Structures and Physical Properties of CdSe Quantum Nanodots. Descriptive Note : Final rept. ...
... Accession Number : ADA270577. Title : Ab Initio Potential Energy Surface for the H + OCS Reaction. Descriptive Note : Final rept. ...
