Functional

In OpenMX, local density approximations (LDA, LSDA) [2,3,4] and a generalized gradient approximation (GGA) [5] to exchange-correlation functional are used. Using a keyword 'scf.XcType', you can choose an approximation to exchange-correlation functional:

  scf.XcType                  LDA        # LDA|LSDA-CA|LSDA-PW|GGA-PBE

Currently, 'LDA', 'LSDA-CA', 'LSDA-PW', and 'GGA-PBE' are available, where 'LSDA-CA' is the local spin density functional of Ceperley-Alder [2], 'LSDA-PW' is the local spin density functional of Perdew-Wang, in which the gradient of density is set in zero in their GGA formalism [4]. Note: 'LSDA-CA' is faster than 'LSDA-PW'. 'GGA-PBE' is GGA proposed by Perdew, Burke, and Ernzerhof [5]. The GGA is implemented by using the first order finite difference method in real space. The relevant keyword to specify the spin (un)polarized and non-collinear calculations is 'scf.SpinPolarization'.

  scf.SpinPolarization        off        # On|Off|NC

If the calculation for the spin polarization is performed, then specify 'ON'. If the calculation for the non-spin polarization is performed, then specify 'OFF'. When you use LDA for the keyword 'scf.XcType' the keyword 'scf.SpinPolarization' must be off. In addition to these options, 'NC' is supported for the non-collinear DFT calculation. For this calculation, see also the Section 'Non-collinear DFT'. In addition, LDA+U functionals are also available. For the details, see the Section 'LDA+U'.