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Configuration selection and extrapolation in multireference configuration interaction calculations: The (H 2 ) 2 van der waals complex as a benchmark example
Author(s) -
Shavitt Isaiah,
Brown Franklin B.,
Burton Peter G.
Publication year - 1987
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560310321
Subject(s) - extrapolation , van der waals force , configuration interaction , multireference configuration interaction , wave function , atomic orbital , complete active space , basis set , truncation (statistics) , full configuration interaction , chemistry , benchmark (surveying) , atomic physics , computational chemistry , physics , quantum mechanics , mathematics , mathematical analysis , molecule , statistics , excited state , electron , density functional theory , geodesy , geography
Multireference configuration interaction (MR‐CI) calculations using energy‐selected and complete‐active‐space reference configurations are compared for a large‐basis‐set treatment of the (H 2 ) 2 van der Waals complex in a T geometry. Procedures for estimating truncation errors arising from energy threshold selection of configuration state functions and for extrapolating to the full CI limit are tested by comparisons with untruncated calculations and with the full CI energy. The results of these tests show that great care is required in the use of the correction and extrapolation formulas. Optimization of the orbitals of the reference wave function (compared to the use of SCF orbitals) is found to produce order‐of‐magnitude improvement in the results.