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# MIXPRE

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MIXPRE = 0 | 1 | 2 | 3

Default: **MIXPRE** = 1

Description: MIXPRE specifies the metric in the Broyden mixing scheme(IMIX=4).

- MIXPRE=0

- No preconditioning, metric=1

- MIXPRE=1

- "Inverse Kerker" metric with automatically determined BMIX (determined in such a way that the variation of the preconditioning weights covers a range of a factor 20)

- MIXPRE=2

- "Inverse Kerker" metric with automatically determined BMIX (determined in such a way that the variation of the preconditioning weights covers a range of a factor 200)

- MIXPRE=3 (implemented for test purposes;
**not**recommended)

The preconditioning is done only on the total charge density (i.e. up+down component) and not on the magnetization charge density (i.e. up-down component). Up to now we have found that introduction of a metric always improves the convergence speed. The best choice is MIXPRE=1 (i.e. the default).

## Related Tags and Sections

IMIX, INIMIX, MAXMIX, AMIX, BMIX, AMIX_MAG, BMIX_MAG, AMIN, WC