New Adapted Gaussian Basis Sets for the Relativistic Closed Shell Atoms From Helium to Barium Generated With the Generator Coordinate Dirac- Fock Method L. G. M. de MACEDO, 1 N. H. MORGON, 2 R. L. A. HAIDUKE, 1 R. C. BARBOSA, 1 A. B. F. da SILVA 1 1 Departamento de Quı ´mica e Fı ´sica Molecular, Instituto de Quı ´mica de Sa ˜o Carlos, Universidade de Sa ˜o Paulo, C.P. 780, 13560-970, Sa ˜o Carlos, SP, Brazil 2 Instituto de Quı ´mica, Universidade Estadual de Campinas (Unicamp), C.P. 6154, 13083-970, Campinas, SP, Brazil Received 9 January 2004; accepted 26 October 2004 Published online 1 April 2005 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/qua.20555 ABSTRACT: The generator coordinate Dirac-Fock (GCDF) method and the downhill simplex algorithm were applied to generate new adapted Gaussian basis sets for relativistic closed shell atoms from He (Z = 2) to Ba (Z = 56). These new basis sets have a size reduction of about 30% when compared to previous GCDF adapted basis sets, and are as compact as some corresponding nonrelativistic Gaussian basis sets. The truncation error is in a millihartree order of magnitude and the optimization scheme adopted here allowed the l - and l + relativistic symmetries to be different. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem 103: 523–528, 2005 Key words: relativistic Gaussian basis sets; generator coordinate Dirac Fock method; downhill simplex algorithm Correspondence to: A. B. F. da Silva; e-mail: alberico@iqsc.usp.br Contract grant sponsor: FAPESP (Brazilian Agency). International Journal of Quantum Chemistry, Vol 103, 523–528 (2005) © 2005 Wiley Periodicals, Inc.