Hyperbolic cosine functions applied to atomic Roothaan-Hartree-Fock wavefunctions: further improvements

A hyperbolic cosine function is incorporated into a Slater-type radial function with a noninteger principal quantum number n. The new radial basis functions are applied to Roothaan-Hartree-Fock calculations of atoms within the minimal-basis framework. Our systematic study on the neutral atoms from He (Z = 2) to Lr (Z = 103) in their ground states shows that the incorporation of greatly improves the minimal-basis approximation, and the present minimal-basis total energies are lower than the conventional double-zeta energies obtained from Slater-type functions with integer n. Orbital energies are also improved. The present minimal-basis wavefunctions surpass the conventional double-zeta wavefunctions in their accuracy, despite fewer numbers of variational parameters.