3.5 Additional Input Sections

3.5.4 User-Defined Exchange-Correlation Density Functionals
($xc_functional)

If the keyword EXCHANGE = GEN then a DFT calculation will be performed using a user-specified combination of exchange and correlation functional(s), as described in Chapter 4. Custom functionals of this sort can be constructed as any linear combination of exchange and/or correlation functionals that are supported by Q-Chem; see Section 5.4 for a list of supported functionals. The format for the $xc_functional input section is the following:

$xc_functional
   X  exchange_symbol     coefficient
   X  exchange_symbol     coefficient
   ...
   C  correlation_symbol  coefficient
   C  correlation_symbol  coefficient
   ...
   K  coefficient
$end

Note:  The coefficients must be real numbers.