[gpaw-users] Clarification regarding calc.get_xc_difference()

[Zeeshan Ahmad]

Hello GPAW team,

The gpaw/ase interface has a function called get_xc_difference(xc) which can be used to calculate the difference in the xc energy between the xc functional supplied in the argument of this function and the xc functional which was set for the calculator earlier. 

The question is: if we provide an xc functional (as argument) which handles only correlation part like ‘LDA_C_PW’ or ‘GGA_C_PBE’, then what will get_xc_difference(xc) give?

Does it calculate the exchange (x) energy using a default functional or assumes the exchange energy = 0. In other words, if the calculator’s functional was set as ‘vdW-DF’ and we do:

calc.get_xc_difference(‘LDA_C_PW’)

then, will the result be:

Difference = E_LDA_correlation - E_exchange_vdW-DF - E_correlation_vdW-DF ? 

(Here the exchange energy of supplied functional was assumed to be zero)


Thanks,
Zeeshan Ahmad