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Energy Decomposition Scheme (energy + decomposition_scheme)
Selected AbstractsEnergy decomposition scheme for combined ab initio quantum mechanical / molecular mechanical methodsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2005Imre Berente Abstract A new energy decomposition scheme is presented which paves the way toward the accurate and simple treatment of boundary atoms in combined ab initio quantum mechanical / molecular mechanical methods. We extend the wave function beyond the quantum region to a few atoms of the molecular mechanical region, which are linked directly to boundary atoms. Furthermore, we apply an approximate decomposition scheme, which allows calculating the total energy in terms of one-center atomic contributions. Comparisons with reference ab initio calculations are made, and good agreement is obtained for geometry parameters referring to CC, CC, and CX (XO, S, N) bonds at the boundary, as well as for the rotational energy curve of n -butane. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] The interplay between experiment and theory in charge-density analysisACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2004Philip Coppens The comparison of theory and experiment remains a cornerstone of scientific inquiry. Various levels of such comparison applicable to charge-density analysis are discussed, including static and dynamic electron densities, topological properties, d -orbital occupancies and electrostatic moments. The advantages and drawbacks of the pseudoatom multipole are discussed, as are the experimentally constrained wavefunctions introduced by Jayatilaka and co-workers, which combine energy minimization with the requirement to provide a reasonable fit to the X-ray structure factors. The transferability of atomic densities can be exploited through construction of a pseudoatom databank, which may be based on analysis of ab initio molecular electron densities, and can be used to evaluate a host of physical properties. Partitioning of theoretical energies with the Morokuma,Ziegler energy decomposition scheme allows direct comparison with electrostatic interaction energies obtained from electron densities represented by the pseudoatom formalism. Compared with the Buckingham expression for the interaction between non-overlapping densities, the agreement with theory is much improved when a newly developed hybrid EP/MM (exact potential/multipole model) method is employed. [source] One-body energy decomposition schemes revisited: Assessment of Mulliken-, Grid-, and conventional energy density analyses,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2009Yasuaki Kikuchi Abstract We propose a new energy density analysis (EDA) that evaluates atomic contributions of all energy terms, i.e., the kinetic, nuclear-attraction, Coulomb, and Hartree,Fock (HF) exchange and density functional theory (DFT) exchange-correlation energies using the Mulliken-type partitioning. Although widely used DFT exchange-correlation functionals are nonlinear expressions in terms of density, they are decomposed into atomic contributions by focusing the linear part of the density. Numerical assessment on Mulliken-EDA, Grid-EDA, and conventional EDA has been carried out for the G2-1 set. Correlations between HF and DFT exchanges demonstrate that a consistent partitioning of all energy terms is essential for EDA. These numerical results confirm that the present Mulliken-EDA offers a more reasonable picture for the atomization process. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] | ||||||||||