MOLECULAR PHYSICS, vol.112, no.1, pp.35-40, 2014 (SCI-Expanded)
The complete orthonormal sets of psi((alpha)*())-exponential type orbitals (psi((alpha)*())-ETOs) in LCAO approximation are investigated for the determination of the optimal values of integer (- < 2) and non-integer * (- < * < 3) by minimising the total energies in atomic calculations. The Hartree-Fock-Roothaan calculations with the use of different values of indices and * are performed within the framework of the minimal basis sets approximation for the ground states of neutral atoms. It is found for non-integer values of * that the efficiency of psi((alpha)*())-ETOs in total energy calculations, electron density, and its derivative and cusp ratio at the nuclei is much better than the other integer values of . It should be noted that the Coulomb-Sturmian and Lambda ETOs are special classes of (())-ETOs for = 1 and = 0, respectively. The performance of psi((alpha)*())-ETOs in atomic energy calculations is also compared to those obtained by using other ETOs such as Slater and B functions. The optimal non-integer values of * are also determined for each atom examined in this work. It is shown that the notably improvement in the efficiency of psi((alpha)*())-ETOs can be obtained by the use of non-integer * values.