Results 251 to 260 of about 855,474 (292)

Density functional calculations of surface free energies

The Journal of Chemical Physics, 2006
We propose a general method of thermodynamic integration to find the free energy of a surface, where our integration parameter is taken to be the strain on the unit cell of the system (which in the example presented in this paper is simply the extension of the unit cell along the normal to the surface), and the integration is performed over the thermal
H, Fox, A P, Horsfield, M J, Gillan
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Direct calculation of electron density in density-functional theory

Physical Review Letters, 1991
A new approach for the study of ground states of many-electron systems is developed via direct calculation of the density in density-functional theory. Not using the Kohn-Sham equations, the method divides a system into subsystems in physical space and determines the density for each subsystem.
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Density Functional Calculations

2010
Density functional theory is based on the two Hohenberg-Kohn theorems, which state that the ground-state properties of an atom or molecule are determined by its electron density function, and that a trial electron density must give an energy greater than or equal to the true energy (the latter theorem is true only if the exact functional could be used).
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Approximate occupation functions for density-functional calculations

Physical Review B, 1997
The density-functional free energy can be written in a form that is stationary with respect to variations in the occupation function. For this reason it is useful to look for approximate occupation functions that are sufficiently close to the Fermi function that accuracy is not compromised and yet have advantages for computation.
D. M. C. Nicholson, X.-G. Zhang
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Density Functional Calculations of Thermochemical Equilibria

The Journal of Physical Chemistry A, 1998
Computationally practical quantum-mechanical methods are needed in order to determine the ideal-gas thermodynamic properties of moderate-size molecules. In this work, we attempt to utilize density functional theory with B3LYP functional to calculate thermodynamic quantities of organic molecules of moderate sizes and to apply the results to characterize
Hansong Cheng, Vipul S. Parekh, John W. Mitchell, Kathryn S. Hayes   +3 more
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Density Functional Calculations of Molecular Bond Energies

The Journal of Chemical Physics, 1986
The calculation of molecular bond energies is a sensitive test of exchange-correlation approximations in density functional theory. The well known local density approximation (LDA) gives excellent bond lengths and vibrational frequencies, but seriously overestimates dissociation energies.
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Large Scale Density Functional Calculations

2004
New developments in algorithms for density functional calculations within the Kohn-Sham methods allow to study systems with several hundreds of atoms. We present a linear scaling method for the construction of the Kohn-Sham Hamiltonian based on fast Fourier transforms.
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Density Functional Calculations for Atomic Clusters

1984
The calculation of the adiabatic ground state energy \( {\text{E}}\left[ {\{ \vec R_{\text{i}} \} } \right] \) of molecules, a long-standing problem in chemistry, is traditionally handled in one of two ways. Quantum chemists employ ab initio methods (meaning one or another brand of CI) which lead in principle to an exact solution of the many-electron ...
J. Harris, J. E. Müller
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Accurate density functional calculations on large systems

International Journal of Quantum Chemistry, 1996
Efforts to compute accurate all-electron density-functional energies for large molecules and clusters using Gaussian basis sets are reviewed and their use in fullerene science described. The foundation of this effort, variational fitting, is described first.
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Density functional calculations on heterocyclic compounds.

Tetrahedron, 1994
Abstract Density functional calculations at LSD, NLSD/6-31G*, DZVP2 levels were performed on azoles, azines and their protonated forms. Geometries and dipole moments were well described by both global bases. Energies obtained at NLSD(BP)/DZVP2 level are reasonably comparable with high level ab initio and experimental data.
Péter Mátyus, Kaoru Fuji, Kiyoshi Tanaka   +2 more
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