A nondiagonal quasidegenerate fourth-order perturbation theory

Kuhler, Kathleen; Hoffmann, Mark R.

doi:10.1007/bf01165353

Cited by 5 publications

(3 citation statements)

References 35 publications

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“…If the P -Q interactions are considered to first-order ͑in the wave function͒ using a nondiagonal variant of QDPT, 18 where the block-diagonal part of the Hamiltonian matrix in the L P L Q space is considered as the unperturbed Hamiltonian, H 0 ϭ PHPϩQHQ, while the off-diagonal block, V ϭ PHQϩQHP, is considered as a perturbation ͓i.e., Kuhler and Hoffmann's ͑KH͒ QDPT ͑Ref. 18͔͒ basic Eqs.…”

Section: ͑2͒mentioning

confidence: 99%

“…In a series of short articles beginning approximately 10 years ago, one of the authors suggested several variants of quasidegenerate perturbation theory, 4,[15][16][17][18] which, in contrast to other QDPTs and MRPTs, were both state-selective and of the ''perturb-then-diagonalize'' type. Not surprisingly, the combination of these two characteristics made the suggested variants quite accurate ͑considering only first-order corrections to the dynamic electron correlation͒ as evidenced by model study calculations.…”

Section: Introductionmentioning

confidence: 99%

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Explication and revision of generalized Van Vleck perturbation theory for molecular electronic structure

Khait

Song

Hoffmann

2002

The Journal of Chemical Physics

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107

100

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The electronic structure of the triiodide ion from relativistic correlated calculations: A comparison of different methodologies J. Chem. Phys. 133, 064305 (2010); 10.1063/1.3474571 Relativistic quasidegenerate perturbation theory with four-component general multiconfiguration reference functionsThe 1 2 A 1 , 1 2 B 2 , and 1 2 A 2 states of the SO 2 + ion studied using multiconfiguration second-order perturbation theory Generalized molecular mechanics including quantum electronic structure variation of polar solvents. I. Theoretical formulation via a truncated adiabatic basis set description

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Section: ͑2͒mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Explication and revision of generalized Van Vleck perturbation theory for molecular electronic structure

Khait

Song

Hoffmann

2002

The Journal of Chemical Physics

Self Cite

107

100

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“…It is clear that representation (24) can also be obtained using a conventional configuration technique. Moreover, such configuration representation of the Hamiltonian matrix is well known and has been actively used in several variants of effective Hamiltonian theory 22–24. However, macroconfiguration representation (24) has greater computational promise than its configuration analog because now the list of configurations is organized in such a way that all configurations of a given macroconfiguration are contiguous.…”

Section: Macroconfiguration‐based Screeningmentioning

confidence: 99%

Macroconfigurations in molecular electronic structure theory

Khait

Song

Hoffmann

2004

Int J of Quantum Chemistry

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Based on the well-known idea of dividing a molecular orbital set into groups, and imposing restrictions on allowed group occupancies, a more general formalism, which we refer to as the macroconfiguration approach, is developed. The approach is shown to be useful in four complementary contexts: First, as with previous uses of orbital groupings, physical considerations can actively be taken into account in constructing configuration spaces; second, the approach is demonstrated to enable the screening of a vast number of noninteracting electron configuration pairs in a computationally efficient manner; third, all advantages of the Table-configuration interaction (CI) technique can be used effectively for evaluating Hamiltonian matrix elements between interacting configurations; finally, the macroconfiguration technique provides an efficient way of regenerating excited configurations as needed in a calculation. These characteristics indicate that the suggested approach is promising for improving the computational efficiency of methods describing electron dynamic correlation and, in particular, for CI calculations involving highly (e.g., triply and quadruply) excited configurations and for methods of effective Hamiltonian theory. The advantages of the suggested technique are illustrated by the results of calculations on the ground and excited states of the difluorodioxirane (CF 2 O 2 ) molecule at the secondorder generalized Van Vleck perturbation theory (GVVPT2) level.

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