and become more satisfying. The other group for the basis set is minimal basis sets, represented by STO-NG (N is the number of GTOs utilised). The main difference between GTOs and STOs is that the variable "r" in the exponential function is squared for GTOs. Also, combinations of them can yield knowledge about a system. A good example is joining three d-type Cartesian GTOs, which generate a Cartesian GTO of s-type . GTOs are inferior to STOs in three cases: