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| {{TAGDEF|LMAXFOCKAE|[integer]|-1}} | | {{TAGDEF|LMAXFOCKAE|[integer]}} |
| {{DEF|ICHARG|2|if {{TAG|ISTART}}{{=}}0|0|else}} | | {{DEF|LAXMFOCKAE|-1|for DFT, Hartree-Fock | 4 | for post DFT methods}} |
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| {{TAGDEF|NMAXFOCKAE|0{{!}}1{{!}}2}} | | Description: {{TAG|LMAXFOCKAE}} determines whether |
| {{DEF|NMAXFOCKAE|0|density functional theory|1|post DFT methods}} | | the overlap densities in the Fock exchange and correlated wave function methods are accurately reconstructed on the plane wave grid or not. Details can be found in the section {{TAG|NMAXFOCKAE}}. |
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| Description: {{TAG|LMAXFOCKAE}} and {{TAG|LMAXFOCKAE}} describes the maximum angular momentum quantum number ''l'' and the number of channels for an "accurate" augmentation of charge densities in Hartree-Fock type routines.
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| ---- | | ---- |
| In the PAW method the difference between the charge density of the all-electron partial waves and
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| the pseudo partial waves
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| <math>
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| Q_{\alpha\beta}(r)= \phi^*_\alpha(r)\phi_\beta(r) - \tilde \phi^*_\alpha(r)\tilde \phi_\beta(r)
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| </math>
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| is usually restored on spherical grids centered at each atom
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| (one-center terms inside the PAW spheres). To describe long range electrostatic terms, the
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| the ''moments'' of the differences of the all-electron and pseudo charge density are also
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| restored on the plane wave grid up to a certain ''l'' quantum number (see {{TAG|LMAXFOCK}}).
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| For the RPA, GW, and most post DFT methods, the one-center terms are presently,
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| however, not implemented. Depending on the material, this can cause sizable errors
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| in particular for 3d and (to a lesser extent) 2p, 4d and 5d elements.
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| To correct for this error, an alternative treatment is implemented
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| on the plane wave grid. This allows to restore the ''shape'' of the charge density difference accurately on the plane wave grid, using the flags {{TAG|LMAXFOCKAE}} and {{TAG|NMAXFOCKAE}}.
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| To achieve this, <math> Q_{\alpha\beta}(r) </math> is Fourier transformed
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| to reciprocal space <math> Q_{\alpha\beta}(q) </math> and then expanded
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| in a set of orthogonal functions localized at each atomic site.
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| If the {{TAG|NMAXFOCKAE}}=0 (the default for DFT and Hartree-Fock calculations), only the moment and of the all-electron charge density is restored on the plane wave grid. This setting is exact for density functional theory, Hartree-Fock as well
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| as hybrid functionals, since the one-center terms are implemented.
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| If the {{TAG|NMAXFOCKAE}}=1 is set, the moments of the all-electron charge density are stored on the plane wave grid. Furthermore, the all-electron charge density is restored up to a typical plane wave energy of 140 eV. This setting yields very accurate results for post DFT methods (MP2, RPA, GW, etc.) for most sp bonded materials. {{TAG|LMAXFOCKAE}} can be used to specify the maximum spherical (l) quantum number up
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| to which this more accurate treatment is used. The default for {{TAG|LMAXFOCKAE}} is 4.
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| If {{TAG|NMAXFOCKAE}}=2 is set, the charge density is restored accurately on the plane wave grid up to a typical plane wave energies of 380 eV. As before, {{TAG|LMAXFOCKAE}} can be used to specify the maximum spherical (l) quantum number up
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| to which this more accurate treatment is used. {{TAG|NMAXFOCKAE}}=2 yields very accurate results for
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| post DFT methods (MP2, RPA, GW) even for difficult 3d elements. For RPA and MP2 total energy calculations, differences between {{TAG|NMAXFOCKAE}}=1 and {{TAG|NMAXFOCKAE}}=2 are usually tiny for total energy differences. Since the absolute correlation energies might change, it is vital to use the same setting for
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| {{TAG|NMAXFOCKAE}} and {{TAG|LMAXFOCKAE}}, if energy differences are calculated.
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| For GW calculations, increasing {{TAG|NMAXFOCKAE}}=1 to {{TAG|NMAXFOCKAE}}=2 might change QP energies by 100-200 meV for 3d and late 4d and 5d elements.
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| If {{TAG|NMAXFOCKAE}} is used, the setting for {{TAG|LMAXFOCKAE}} should be also checked. Generally, it suffices to set {{TAG|LMAXFOCKAE}} to twice the maximum ''l'' quantum number found in the {{FILE|POTCAR}} file.
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| For instance for sp elements, {TAG|LMAXFOCKAE}} = 2 suffices. For d elements, {TAG|LMAXFOCKAE}} = 4 suffices
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| (a d electron can create a density with l-quantum number of 4), whereas for f elements, users
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| should test whether {TAG|LMAXFOCKAE}} = 4 is required.
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| == Related Tags and Sections == | | == Related Tags and Sections == |
| {{TAG|LMAXFOCK}} | | {{TAG|LMAXFOCK}} {{TAG|NMAXFOCKAE}} |
| ---- | | ---- |
| [[The_VASP_Manual|Contents]] | | [[The_VASP_Manual|Contents]] |
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| [[Category:INCAR]][[Category:Hybrids]] | | [[Category:INCAR]][[Category:Hybrids]] |
LMAXFOCKAE = [integer]
| Default: LAXMFOCKAE
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= -1
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for DFT, Hartree-Fock
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= 4
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for post DFT methods
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Description: LMAXFOCKAE determines whether
the overlap densities in the Fock exchange and correlated wave function methods are accurately reconstructed on the plane wave grid or not. Details can be found in the section NMAXFOCKAE.
Related Tags and Sections
LMAXFOCK NMAXFOCKAE
Contents
