Distributed Gaussian basis sets: Variationally optimized s-type sets for the open-shell systems HeH and BeH

Distributed basis sets of s-type Gaussian functions are determined by invoking the variation principle for the restricted open-shell matrix Hartree-Fock ground states of the open-shell molecular systems HeH and BeH for nuclear separations of 1.500 bohr and 2.500 bohr, respectively. The calculated energy expectation values supported by these distributed basis sets are compared with the energies obtained from finite difference open-shell Hartree-Fock calculations. The restricted open-shell matrix Hartree-Fock calculations are performed by means of the asymptotic method. The accuracy of the approximations to the energy expectation values supported by the distributed basis sets of s-type Gaussian functions is comparable with that attained in previous studies of closed-shell systems. The parameters, that is, the exponents and positions defining the variationally optimized distributed basis sets, are presented and discussed. (C) 2004 Wiley Periodicals, Inc.