SLATER WAVE FUNCTIONS
We have just explained that the wave equation for the helium atom cannot be solved exactly because
of the term involving 1/ r 12 . If the repulsion between two electrons prevents a wave equation from
being solved, it should be clear that when there are more than two electrons the situation is worse. If
there are three electrons present (as in the lithium atom) there will be repulsion terms involving 1/ r 12 ,
1/ r 13 , and 1/ r 23 . Although there are a number of types of calculations that can be performed (particularly the self-consistent fi eld calculations), they will not be described here. Fortunately, for some situations, it is not necessary to have an exact wave function that is obtained from the exact solution of a wave equation. In many cases, an approximate wave function is suffi cient. The most commonly used approximate wave functions for one electron are those given by J. C. Slater, and they are known as
Slater wave functions or Slater-type orbitals (usually referred to as STO orbitals).