ENCUTGWSOFT: Difference between revisions

Revision as of 14:15, 14 March 2017

ENCUTGWSOFT = [real] (energy cutoff for response function)

Default: ENCUTGWSOFT	= ENCUTGW $\times 0.8$	for ALGO=ACFDT
	= ENCUTGW	else

Descprition: The flag 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: ${\displaystyle v_{\bold{G}} = \frac{4 \pi e^2} {| \bold{G}|^2} \frac{1}{2} \left( 1 + \cos \left( \pi \, \frac{ \frac{\hbar^{2} |\bold{G}|^2 }{2 m_e} - \mathbf{ ENCUTGWSOFT} }{ \mathbf{ENCUTGW} - \mathbf{ENCUTGWSOFT}} \right) \right) \qquad \mbox{for} \quad \frac{\hbar^2 |\bold{G}|^2 }{2 m_e} > \mathbf{ENCUTGWSOFT}}$

Related Tags and Sections

PRECFOCK, ENCUT, ENCUTGW, GW calculations

Contents

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