LSCK

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

If LSCK is set to .TRUE., the squeezed Coulomb kernel is used instead of the cosine window:^[1]

[math]\displaystyle{ v_{G} = 4 \pi e^2 \frac{ (G_{max}-G_{min})(G_{max}-G) }{ (G_{min}^2 - G(2G_{min}-G_{max}))^2 } \qquad \mbox{for} \quad \mathrm{ENCUTGWSOFT}=\frac{\hbar^2G_{min}^2}{2m_e}\lt \frac{\hbar^2 G^2}{2m_e}\lt \frac{\hbar^2G_{max}^2}{2m_e}=\mathrm{ENCUTGW} }[/math]

This kernel squeezes contributions from large wave vectors [math]\displaystyle{ G\gt G_{max} }[/math] into the window given by ENCUTGWSOFT. Effectively, this extrapolates the RPA correlation energy to the ENCUTGW [math]\displaystyle{ \to \infty }[/math] limit, assuming that the basis set incompleteness error falls off as [math]\displaystyle{ 1/\mathrm{ENCUTGW}^{3/2} }[/math].