LMAXFOCK: Difference between revisions
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Description: {{TAG|LMAXFOCK}} sets the maximum angular momentum quantum number ''l'' for the augmentation of charge densities in Hartree-Fock type routines. | Description: {{TAG|LMAXFOCK}} sets the maximum angular momentum quantum number ''l'' for the augmentation of charge densities in Hartree-Fock type routines. | ||
---- | ---- | ||
This | In the PAW method, the difference between the charge density of the all-electron partial waves and | ||
the pseudo partial waves | |||
<math> | |||
Q_{\alpha\beta}(r)= \phi^*_\alpha(r)\phi_\beta(r) - \tilde \phi^*_\alpha(r)\tilde \phi_\beta(r) | |||
</math> | |||
is usually restored on spherical grids centered at each atom | |||
(one-center terms inside the PAW spheres). To describe long range electrostatic terms, the ''moments'' of the differences of the all-electron and pseudo charge density | |||
also need to added on the plane wave grid. This is done up to a certain ''l'' quantum number. | |||
These augmentation charges restore the moments of the all-electron density on the plane wave | |||
grid. For the charge density, this augmentation is done exactly up to the maximum | |||
''l'' quantum number required for the POTCAR files. | |||
This flag determines the treatment on the plane wave grid for | |||
the exact exchange. | |||
To compensate resulting errors, the contributions from the one-center terms are evaluated for the pseudo orbitals also only up to ''l''={{TAG|LMAXFOCK}}, whereas the one-center terms for the exact all-electron orbitals are evaluated up to the maximum required ''l'' (twice the angular quantum number of the partial wave with the highest ''l''). The default is {{TAG|LMAXFOCK}}=4, and it might be required to increase this parameter, if the system contains f-electrons. Since this increases the computational load considerably (factor 2), it is recommended to perform tests, whether the results are already reasonably converged using the default {{TAG|LMAXFOCK}}=4. | |||
To be compatible w.r.t. old releases, VASP also reads the flag {{TAG|HFLMAX}} to the same effect as {{TAG|LMAXFOCK}}. | To be compatible w.r.t. old releases, VASP also reads the flag {{TAG|HFLMAX}} to the same effect as {{TAG|LMAXFOCK}}. | ||
Revision as of 15:56, 14 March 2017
LMAXFOCK = [integer]
Default: LMAXFOCK = 4
Description: LMAXFOCK sets the maximum angular momentum quantum number l for the augmentation of charge densities in Hartree-Fock type routines.
In the PAW method, the difference between the charge density of the all-electron partial waves and the pseudo partial waves is usually restored on spherical grids centered at each atom (one-center terms inside the PAW spheres). To describe long range electrostatic terms, the moments of the differences of the all-electron and pseudo charge density also need to added on the plane wave grid. This is done up to a certain l quantum number. These augmentation charges restore the moments of the all-electron density on the plane wave grid. For the charge density, this augmentation is done exactly up to the maximum l quantum number required for the POTCAR files.
This flag determines the treatment on the plane wave grid for
the exact exchange.
To compensate resulting errors, the contributions from the one-center terms are evaluated for the pseudo orbitals also only up to l=LMAXFOCK, whereas the one-center terms for the exact all-electron orbitals are evaluated up to the maximum required l (twice the angular quantum number of the partial wave with the highest l). The default is LMAXFOCK=4, and it might be required to increase this parameter, if the system contains f-electrons. Since this increases the computational load considerably (factor 2), it is recommended to perform tests, whether the results are already reasonably converged using the default LMAXFOCK=4.
To be compatible w.r.t. old releases, VASP also reads the flag HFLMAX to the same effect as LMAXFOCK.