character(len=15) :: xc_functional

The functional to use when calculating the exchange-correlation potential. Possible values are:

• LDA - Local Density Approximation
• PW91 - Perdew Wang '91 GGA
• PBE - Perdew Burke Ernzerhof
• RPBE - Revised Perdew Burke Ernzerhof
• HF - Hartree-Fock
• SHF - Screened Hartree-Fock
• EXX - Exact exchange
• SX - Screened exchange
• ZERO - No exchange-correlation potential
• HF-LDA -LDA with exchange contribution replaced by Hartree-Fock
• SHF-LDA - -LDA with exchange contribution replaced by screened Hartree-Fock
• EXX-LDA - -LDA with exchange contribution replaced by exact exchange
• SX-LDA - LDA with exchange contribution replaced by screeened exchange

The default value of this parameter is `LDA'.