ALGO for response functions and GW calculations

 ALGO   = CHI | GW0 | GW | scGW |  scGW0

Default: none. The input string is parsed case insensitive.

ALGO = CHI calculates the response functions only. For ALGO = GW and ALGO = GW0 the wavefunctions of the previous groundstate calculations are maintained, and G$_0$W$_0$ calculations are performed. If NELM is set, several interations are performed, and the eigenvalues are updated in the calculation of G ( ALGO = GW0) or W and G ( ALGO = GW). A full update of the wavefunctions can be performed by specifying ALGO = SCGW and ALGO = SCGW0. In the former case, the wavefunctions and eigenvalues are updated for the calculations of G and W, whereas in the latter case the wavefunctions and eigenvalues are only updated in G.