8.4 User-Defined Basis Sets ($basis)

8.4.2 Job Control

In order to use a user-defined basis set the BASIS $rem must be set to GENERAL or GEN.

When using a non-standard basis set which incorporates d or higher angular momentum basis functions, the $rem variable PURECART needs to be initiated. This $rem variable indicates to the Q-Chem program how to handle the angular form of the basis functions. As indicated above, each integer represents an angular momentum type which can be defined as either pure (1) or Cartesian (2). For example, 111 specifies that d, f and g basis functions should have pure form whereas 121 indicates that d- and g-functions are pure but f functions are Cartesian. These three-digit codes can be used even if the basis does not contain g functions; PURECART = 111 (or 222) specifies to use pure (or Cartesian) functions for all angular momentum types.

       Controls the use of pure (spherical harmonic) or Cartesian angular forms
       2111 Cartesian h-functions and pure g,f,d functions
       hgfd Use 1 for pure and 2 for Cartesian.
       This is pre-defined for all standard basis sets

In standard basis sets all functions are pure, except for the d functions in n-21G–type bases (e.g., 3-21G) and n-31G bases (e.g., 6-31G, 6-31G*,6-31+G*, ). In particular, the 6-311G series uses pure functions for both d and f.