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Accurate CI expansion in a spline basis of the helium ground‐state wave function
Author(s) -
Decleva Piero,
Lisini Adriana,
Venuti Marco
Publication year - 1995
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.560560106
Subject(s) - wave function , ground state , helium , basis (linear algebra) , basis function , physics , function (biology) , atomic physics , mathematics , quantum mechanics , geometry , evolutionary biology , biology
Abstract Careful study of radial spline basis‐set convergence on the angular limits of the He 1s 2 state has been performed. Improvement of algorithm allows reaching the full ci limit in a large radial (79 spline functions) and angular (I max =80) expansion. A variational energy of − 2.903724299061 au, with an error of 7.8 × 10 −8 au is obtained, improving by over two orders of magnitude the previous available limit. Accurate angular momentum limits (1 × 10 −8 au) are obtained up to l = 25. Analysis of the behavior of two‐particle radial wave functions reveals a sharply peaked behavior which allows effective truncation of the two‐electron radial basis for high angular momentum values. A reasonable estimate of computational resources required indicate that an accuracy below 1 × 10 −8 au is presently feasible and about 1 × 10 −9 au possible in the near future. © 1995 John Wiley & Sons, Inc.