Currently three different exchange-correlation functionals are implemented: LDA (Ceperley-Alder) and GGA (Perdew-Wang 91, Perdew Burke Ernzerhof). Spin polarized calculation is supported in all cases. You can set the exchange-correlation functional with:
exchange_correlation name_of_functional.
By default:
exchange_correlation ceperley_alder
The GGA can be switched on with:
exchange_correlation perdew_wang_91 or
exchange_correlation perdew_burke_ernzerhof
The shortened forms pw91 and pbe are also recognised options to exchange_correlation.
Note that for spin-polarized calculation you should put the following line in "input" file
number_of_spins 2
For non-spin-polarized calculation you should put
number_of_spins 1 (This is default)
Note that direct minimization (optimize insulator option) is not supported for spin-polarized calculation.