ENCUTGWSOFT: Difference between revisions
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{{TAGDEF|ENCUTGWSOFT|[real] | {{TAGDEF|ENCUTGWSOFT|[real]}} | ||
{{DEF|ENCUTGWSOFT|{{TAG|ENCUTGW}}<math>\times 0.8</math>| for {{TAG|ALGO}}{{=}}''ACFDT''|{{TAG|ENCUTGW}}<math>\times 0.8</math>| as of VASP.6.3 | {{TAG|ENCUTGW}}|else}} | |||
{{NB|important|For vasp.6.3 and later releases {{TAG|ENCUTGWSOFT}} always defaults to {{TAG|ENCUTGW}}<math>\times 0.8</math>.}} | |||
Descprition: The flag {{TAG|ENCUTGWSOFT}} sets the energy cutoff for response function, such that it allows to truncate the Coulomb kernel slowly between the energy | |||
specified by {{TAG|ENCUTGWSOFT}} and {{TAG|ENCUTGW}} using a cosine window function. | |||
---- | |||
RPA/ACFDT correlation energies converge very slowly with respect to <math>\mathbf{G}_{\rm max }</math>. | |||
Thus VASP automatically extrapolates to the infinite basis set limit using a linear regression to the equation: {{cite|harl:2008}}{{cite|harl:2010}}{{cite|klimes:2014}} | |||
<math>E_{\mathrm{c}}({\mathbf{G}})=E_{\mathrm{c}}(\infty)+\frac{A}{{\mathbf{G}}^3}</math>. | |||
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_{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 {{TAG|LSCK}} is set to .TRUE., the squeezed Coulomb kernel is used instead of the cosine window:{{cite|riemelmoser:jcp:2020}} | |||
<math>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}<\frac{\hbar^2 G^2}{2m_e}<\frac{\hbar^2G_{max}^2}{2m_e}=\mathrm{ENCUTGW}</math> | |||
== Related | This kernel ''squeezes'' contributions from large wave vectors <math>G>G_{max}</math> into the window given by {{TAGBL|ENCUTGWSOFT}}. | ||
{{NB|mind|The infinite basis set limit extrapolation for RPA/ACFDT is described in more detail [[ACFDT/RPA_calculations#Basis_set_convergence|here]].}} | |||
== Related tags and articles == | |||
{{TAG|PRECFOCK}}, | {{TAG|PRECFOCK}}, | ||
{{TAG|ENCUT}}, | {{TAG|ENCUT}}, | ||
{{TAG|ENCUTGW}}, | {{TAG|ENCUTGW}}, | ||
{{TAG|GW calculations}} | {{TAG|GW calculations}}, | ||
{{TAG|LSCK}}, | |||
[[ACFDT/RPA_calculations#Basis_set_convergence|RPA/ACFDT basis set convergence]], | |||
{{sc|ENCUTGWSOFT|Examples|Examples that use this tag}} | |||
---- | ---- | ||
[[Category:INCAR]][[Category:GW]] | [[Category:INCAR tag]][[Category:Many-body perturbation theory]][[Category:GW]] |
Latest revision as of 14:18, 24 April 2023
ENCUTGWSOFT = [real]
Default: ENCUTGWSOFT | = ENCUTGW | for ALGO=ACFDT |
= ENCUTGW | as of VASP.6.3 | |
= ENCUTGW | else |
Important: For vasp.6.3 and later releases ENCUTGWSOFT always defaults to ENCUTGW. |
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 using a cosine window function.
RPA/ACFDT correlation energies converge very slowly with respect to . Thus VASP automatically extrapolates to the infinite basis set limit using a linear regression to the equation: [1][2][3]
.
This usually leads to much smoother energy-volume curves in ACFDT calculations and MP2 calculations. The modified Coulomb kernel is in this case:
If LSCK is set to .TRUE., the squeezed Coulomb kernel is used instead of the cosine window:[4]
This kernel squeezes contributions from large wave vectors into the window given by ENCUTGWSOFT.
Mind: The infinite basis set limit extrapolation for RPA/ACFDT is described in more detail here. |
Related tags and articles
PRECFOCK, ENCUT, ENCUTGW, GW calculations, LSCK, RPA/ACFDT basis set convergence, Examples that use this tag