AMIX: Difference between revisions
No edit summary |
No edit summary |
||
| (One intermediate revision by one other user not shown) | |||
| Line 7: | Line 7: | ||
eigenvalues of (default mixing * dielectric matrix) | eigenvalues of (default mixing * dielectric matrix) | ||
The parameters for the mixing are optimal if the mean eigenvalue Γ<sub>mean</sub>=1, and if the width of the eigenvalue spectrum is minimal. For an initial linear mixing ({{TAG|BMIX}}≈0) an optimal setting for {{TAG|AMIX}} can be found easily by setting {{TAG|AMIX}}<sub>optimal</sub>={{TAG|AMIX}}<sub>current</sub>*Γ<sub>mean</sub>. For the Kerker scheme ({{TAG|IMIX}}=1) either {{TAG|AMIX}} or {{TAG|BMIX}} can be optimized, but we recommend to change only {{TAG|BMIX}} and keep {{TAG|AMIX}} fixed (you must decrease {{TAG|BMIX}} if the mean eigenvalue is larger than one, and increase {{TAG|BMIX}} if the mean eigenvalue Γ<sub>mean</sub><1). | The parameters for the mixing are optimal if the mean eigenvalue Γ<sub>mean</sub>=1, and if the width of the eigenvalue spectrum is minimal. For an initial linear mixing ({{TAG|BMIX}}≈0) an optimal setting for {{TAG|AMIX}} can be found easily by setting {{TAG|AMIX}}<sub>optimal</sub>={{TAG|AMIX}}<sub>current</sub>*Γ<sub>mean</sub>. For the Kerker scheme ({{TAG|IMIX}}=1) either {{TAG|AMIX}} or {{TAG|BMIX}} can be optimized, but we recommend to change only {{TAG|BMIX}} and keep {{TAG|AMIX}} fixed (you must decrease {{TAG|BMIX}} if the mean eigenvalue is larger than one, and increase {{TAG|BMIX}} if the mean eigenvalue Γ<sub>mean</sub><1). | ||
However, the optimal {{TAGBL|AMIX}} depends very much on the system, for metals this parameter usually has to be rather small, e.g. AMIX= 0.02. | |||
== Related Tags and Sections == | == Related Tags and Sections == | ||
| Line 24: | Line 25: | ||
[[The_VASP_Manual|Contents]] | [[The_VASP_Manual|Contents]] | ||
[[Category:INCAR]][[Category:Electronic Minimization]][[Category:Mixing]] | [[Category:INCAR]][[Category:Electronic Minimization]][[Category:Density Mixing]] | ||
Revision as of 07:40, 1 September 2020
AMIX = [real]
| Default: AMIX | = 0.8 | if ISPIN=1 and one uses US-PPs |
| = 0.4 | if ISPIN=2 and one uses US-PPs | |
| = 0.4 | if one uses PAW datasets |
Description: AMIX specifies the linear mixing parameter.
In VASP the eigenvalue spectrum of the charge dielectric matrix is calculated and written to the OUTCAR file at each electronic step. This allows a rather easy optimization of the mixing parameters, if required. Search in the OUTCAR file for
eigenvalues of (default mixing * dielectric matrix)
The parameters for the mixing are optimal if the mean eigenvalue Γmean=1, and if the width of the eigenvalue spectrum is minimal. For an initial linear mixing (BMIX≈0) an optimal setting for AMIX can be found easily by setting AMIXoptimal=AMIXcurrent*Γmean. For the Kerker scheme (IMIX=1) either AMIX or BMIX can be optimized, but we recommend to change only BMIX and keep AMIX fixed (you must decrease BMIX if the mean eigenvalue is larger than one, and increase BMIX if the mean eigenvalue Γmean<1). However, the optimal AMIX depends very much on the system, for metals this parameter usually has to be rather small, e.g. AMIX= 0.02.
Related Tags and Sections
IMIX, INIMIX, MAXMIX, BMIX, AMIX_MAG, BMIX_MAG, AMIN, MIXPRE, WC