LSCK

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

Important: Up to vasp.6.2, the default was LSCK= .TRUE.

Description: LSCK=.True. switches on the squeezed Coulomb kernel.

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

$v_{G}=4\pi e^{2}{\frac {(G_{max}-G_{min})(G_{max}-G)}{(G_{min}^{2}-G(2G_{min}-G_{max}))^{2}}}\qquad {\mbox{for}}\quad \mathrm {ENCUTGWSOFT} ={\frac {\hbar ^{2}G_{min}^{2}}{2m_{e}}}<{\frac {\hbar ^{2}G^{2}}{2m_{e}}}<{\frac {\hbar ^{2}G_{max}^{2}}{2m_{e}}}=\mathrm {ENCUTGW}$

This kernel 'squeezes' the contributions from large wave vectors $G>G_{max}$ into the window given by ENCUTGWSOFT. Effectively, this extrapolates the random-phase-approximation–correlation energy to the ENCUTGW $\to \infty$ limit, assuming that the basis-set-incompleteness error falls off as $1/$ ENCUTGW $^{3/2}$ .

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