Specifying Basis Sets

PSI3 uses basis sets comprised of Cartesian or spherical harmonic Gaussian functions. A basis set is identified by a string, enclosed in double quotes. Currently, there exist three ways to specify which basis sets to use for which atoms:

• basis = string - all atoms use basis set type.
• basis = (string1 string2 string3 ... stringN) - string i specifies the basis set for atom i. Thus, the number of strings in the basis vector has to be the same as the number of atoms (including ghost atoms but excluding dummy atoms). Another restriction is that symmetry equivalent atoms should have same basis sets, otherwise input will use the string provided for the so-called unique atom out of the set of symmetry equivalent ones.

•   basis = (
      (element1 string1)
      (element2 string2)
              ...
      (elementN stringN)
    )
  

  string i specifies the basis set for chemical element element i.