ENCUTGWSOFT

ENCUTGWSOFT = [real]

Default: ENCUTGWSOFT	= ENCUTGW[math]\displaystyle{ \times 0.8 }[/math]	for ALGO=ACFDT
	= ENCUTGW[math]\displaystyle{ \times 0.8 }[/math]	as of VASP.6.3
	= ENCUTGW	else

Important: For vasp.6.3 and later releases ENCUTGWSOFT always defaults to ENCUTGW[math]\displaystyle{ \times 0.8 }[/math].

Descprition: The flag ENCUTGWSOFT sets the energy cutoff for response function, such that it allows to truncate the Coulomb kernel slowly between the energy specified by ENCUTGWSOFT and ENCUTGW.

This usually leads to much smoother energy-volume curves in ACFDT calculations and MP2 calculations. The modified Coulomb kernel is in this case: [math]\displaystyle{ v_{\bold{G}} = \frac{4 \pi e^2} {G^2} \frac{1}{2} \left( 1 + \cos \left( \pi \, \frac{ \frac{\hbar^{2} G^2 }{2 m_e} - \mathrm{ ENCUTGWSOFT} }{ \mathrm{ENCUTGW} - \mathrm{ENCUTGWSOFT}} \right) \right) \qquad \mbox{for} \quad \frac{\hbar^2 G^2 }{2 m_e} > \mathrm{ENCUTGWSOFT} }[/math]

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

[math]\displaystyle{ v_{\bold{G}} = \frac{4 \pi e^2} {| \bold{G}|^2} \frac{1}{2} \left( 1 + \cos \left( \pi \, \frac{ \frac{\hbar^{2} |\bold{G}|^2 }{2 m_e} - \mathrm{ ENCUTGWSOFT} }{ \mathrm{ENCUTGW} - \mathrm{ENCUTGWSOFT}} \right) \right) \qquad \mbox{for} \quad G_{min}<G<G_{max} }[/math]

where [math]\displaystyle{ \hbar^2 G_{max} = \mathrm{ENCUTGW} }[/math]