Possibilities of distributive gaussian $sp$-functions for calculating the correlation energy of molecules in the ground and excited states

The possibilities of distributive bases from Gaussian $sp$-functions for calculating the correlation energy of molecules in the second order $(E^{(2)})$ of the Møller–Plesset perturbation theory (MPPT) have been investigated. The effectiveness of such bases has been demonstrated by comparing the $E^{(2)}$ values obtained in distributive and standard atom-centered bases. Calculations have been performed for both the ground and excited states with ground symmetry. For this purpose, an analog of Møller–Plesset perturbation theory for excited states that preserves its advantages for the ground state has been developed. It has been shown that distributive $sp$-functions provide the accuracy of calculating $E^{(2)}$ that is comparable to that of atom-centered bases including $s$-, $p$-, and $d$-functions.