Electronic structure computations

Ortiz J V 1997 The electron propagator picture of molecular electronic structure Computational Chemistry Reviews of Current Trends vo 2, ed J Leszczynski (Singapore World Scientific) pp 1-61... 

Simply doing electronic structure computations at the M, K, X, and T points in the Brillouin zone is not necessarily sufficient to yield a band gap. This is because the minimum and maximum energies reached by any given energy band sometimes fall between these points. Such limited calculations are sometimes done when the computational method is very CPU-intensive. For example, this type of spot check might be done at a high level of theory to determine whether complete calculations are necessary at that level. 

Electronic structure computations would be greatly simplified by the finding of practical NOFs. One may attempt to approximate the unknown off-diagonal elements of A considering the sum rule (89) and analytic constraints (101) imposed by the D-, G-, and Q-conditions. However, it is not evident how to approach A, for p q, in terms of the ONs. Due to this fact, let s rewrite the energy term, which involves A, as... 

Mueller, Michael R. Fundamentals of Quantum Chemistry Molecular Spectroscopy and Modern Electronic Structure Computations. New York Kluwer Academic/Plenum Publishers, 2001. 

The development that led to the emergence of DFT to its current status as the most widely used electronic structure computational method is that due to KS [274]. The ansatz used by KS replaces the interacting problem with an auxiliary independent particle one, with all the many-body effects included in an exchange-correlation functional. In practice, the KS scheme introduces an equivalent orbital picture (rigorously established), with the resulting KS equations solved self-consistently. 

This chapter is structured as follows In Sect. 6.2, a basic introduction to molecular refinement is presented, stressing particularly relevant aspects. Section 6.3 reviews the recent work by Falklof et al., describing how the 2 x 2 x 2 supercell for the lysozyme structure was obtained. Section 6.4 reviews some modern advances in DFT, focusing on dispersion-corrected DFT, while Sect. 6.5 describes the effects of DFT optimization of atomic coordinates on the agreement between observed and calculated X-ray structure factors. The aim is to determine an optimal electronic-structure computational procedure for quantum protein refinement, and we consider only the effects of minor local perturbations to the existing protein model rather than those that would be produced by allowing full protein refinement. 

Nonadiabatic Computations—Where Theory Delivers MARVEL—An Active Database Approach Electronic structure computations... 

For the purpose of high-accuracy benchmarking, not all CCSD(T) computations are of equal accuracy. Just as in any electronic structure computation, the choice of one-particle basis set matters. 

G. Schaftenaar, J. H. Noordik, Molden a pre- and post-processing program for molecular and electronic structures ,/. Comput.-Aided Mol. Design, 14 (2000), 123. 

Abstract A new recursive procedure is reported for the evaluation of certain three-body integrals involving exponentially correlated atomic orbitals. The procedure is more rapidly convergent than those reported earlier. The formulas are relevant to ab initio electronic-structure computations on three- and four-body systems. They also illustrate techniques that are useful in the evaluation of summations involving binomial coefficients. 

For electronic-structure computations involving exponentially correlated orbitals in atomic systems, it is convenient to generate the necessary integrals using recurrence... 

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