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Routes to full CI through extrapolation in multireference configuration calculations for electronic structures
Author(s) -
Burton Peter G.
Publication year - 1983
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.560230231
Subject(s) - extrapolation , van der waals force , scaling , chemistry , configuration interaction , consistency (knowledge bases) , planar , wave function , coupled cluster , atomic physics , computational chemistry , physics , statistics , mathematics , molecule , computer science , geometry , organic chemistry , computer graphics (images)
“Full CI ” energy extrapolation techniques for use with MRDCI (or MCSCF ‐ CI ) wave function calculations are illustrated for (H 2 ) 2 which is “pathological” [C. F. Jackels and I. Shavitt, Theor. Chim Acta 58 , 81 (1981)]. Our analysis suggests that this extrapolation should be fundamentally more reliable than cluster correction formula results, through the application of a double internal consistency scaling of systematic error estimates, despite explicit treatment of only a small fraction of the configuration list of a full CI. The results of extrapolation suggest that the van der Waals interaction for H 2 –H 2 at R = 6.5 a 0 in the planar T configuration is less than 200 μ H greater than our semiempirical estimate for this interaction strength. Although the role played by the limited basis (80 functions) is not assessed by the present calculations, it appears possible that absolute errors from extrapolation from 16255 SAF results to estimate the full CI value (912464 SAF's) are as small as 0.5 kJ/mol.