Relativistic molecular orbitals, types functions

For the non-relativistic case various functions have been tried, and discussions of their respective merits may be found in the literature [3]. The simplest has been to use hydrogenic functions, or suitably modified La-guerre polynomials. This may be useful for purposes of analysis in simple atomic systems, but has had little impact on the molecular field. The reason for this is the complicated form of the integrals. A somewhat more efficient choice is the Slater type orbital (STO) of the form... 

---