Different Result between Gaussian and GAMESon Same Named Basis Sets

Abstract

Gaussian and GAMESS, which are the codes of the ab initio molecular orbital method, can be used simply by specifying the name of the basis set such as STO-3G. These make a difference in the result in spite of using the same name. It is serious because the results have to be the same using the same input. In this paper, we call attention to the use of both programs with STO-3G for showing hydrides of the third period elements (NaH, MgH2, AlH3, SiH4, PH3, H2S, HCl) to alert users who are conducting research using two programs and the calculated results were comparable. As a result, except for HCl, the total energy and the energy of HOMO were lower in GAMESS than in Gaussian. This is due to the difference in the spatial spread of the 3s orbital and the 3p orbital of the third period element. The Mulliken charge is smaller in GAMESS than in Gaussian. When using some other programs, it is important to examine whether the input data can describe the electronic state intended by the user.