Requests for technical support from the VASP group should be posted in the VASP-forum.

# ODDONLYGW

ODDONLYGW = [logical]
Default: ODDONLYGW = .FALSE.

Description: ODDONLYGW allows to avoid the inclusion of the ${\displaystyle \Gamma }$ point in the evaluation of response functions (in GW calculations).

The independent particle polarizability ${\displaystyle \chi _{{{{\mathbf {q}}}}}^{0}({{\mathbf {G}}},{{\mathbf {G}}}',\omega )}$ is given by:

${\displaystyle \chi _{{{{\mathbf {q}}}}}^{0}({{\mathbf {G}}},{{\mathbf {G}}}',\omega )={\frac {1}{\Omega }}\sum _{{n,n',{{\mathbf {k}}}}}2w_{{{{\mathbf {k}}}}}(f_{{n'{{\mathbf {k}}}+{{\mathbf {q}}}}}-f_{{n{{\mathbf {k}}}}})\times {\frac {\langle \psi _{{n{{\mathbf {k}}}}}|e^{{-i({{\mathbf {q}}}+{{\mathbf {G}}}){{\mathbf {r}}}}}|\psi _{{n'{{\mathbf {k}}}+{{\mathbf {q}}}}}\rangle \langle \psi _{{n'{{\mathbf {k}}}+{{\mathbf {q}}}}}|e^{{i({{\mathbf {q}}}+{{\mathbf {G}}}'){{\mathbf {r'}}}}}|\psi _{{n{{\mathbf {k}}}}}\rangle }{\epsilon _{{n'{{\mathbf {k}}}+{{\mathbf {q}}}}}-\epsilon _{{n{{\mathbf {k}}}}}-\omega -i\eta }}}$

If the ${\displaystyle \Gamma }$ point is included in the summation over ${\displaystyle {\mathbf {k}}}$, convergence is very slow for some materials (e.g. GaAs).

To deal with this problem the flag ODDONLYGW has been included. In the automatic mode, the ${\displaystyle {\mathbf {k}}}$-grid is given by (see Sec. \ref{sec:autok}):

${\displaystyle {\vec {k}}={\vec {b}}_{{1}}{\frac {n_{{1}}}{N_{{1}}}}+{\vec {b}}_{{2}}{\frac {n_{{2}}}{N_{{2}}}}+{\vec {b}}_{{3}}{\frac {n_{{3}}}{N_{{3}}}},\qquad n_{1}=0...,N_{1}-1\quad n_{2}=0...,N_{2}-1\quad n_{3}=0...,N_{3}-1.}$