GW dependence on LRPA parameter and VASP version
Posted: Thu Jan 30, 2014 8:12 pm
I have found VASP 5.2 and 5.3 to exhibit different behaviors when performing GW band gap calculations based on the LRPA parameter. I tested the calculations on MgO which has an experimental band gap of 7.80 eV. Unless otherwise specified, all jobs below were run with an identical setup.
When using VASP 5.2 and explicitly specifying LRPA=.FALSE., the band gap of MgO is found to be 7.86 eV. If LRPA is not specified (with no other changes), the band gap is 8.21 eV. In both cases the OUTCAR gives LRPA=F as is expected since the default value is FALSE.
When using VASP 5.3 and explicitly specifying LRPA=.FALSE., the following error message results "You calculate the electron-hole interaction using AEXX=0. This is hardly what you want to do. Maybe you have forgotten to set AEXX in the INCAR file." I will mention that I am starting from GGA wavefunctions such that there are no exchange parameters in my INCAR. If LRPA is not specified (with no other changes), the band gap is 8.21 eV consistent with VASP 5.2.
When using VASP 5.2 and explicitly specifying LRPA=.FALSE., the band gap of MgO is found to be 7.86 eV. If LRPA is not specified (with no other changes), the band gap is 8.21 eV. In both cases the OUTCAR gives LRPA=F as is expected since the default value is FALSE.
When using VASP 5.3 and explicitly specifying LRPA=.FALSE., the following error message results "You calculate the electron-hole interaction using AEXX=0. This is hardly what you want to do. Maybe you have forgotten to set AEXX in the INCAR file." I will mention that I am starting from GGA wavefunctions such that there are no exchange parameters in my INCAR. If LRPA is not specified (with no other changes), the band gap is 8.21 eV consistent with VASP 5.2.