# CURVY_STEPS

References: Shao2003

Specifies the parameters of the linear scaling SCF routines [Edit on GitHub]

## Keywords

- FILTER_FACTOR

- FILTER_FACTOR_SCALE

- LINE_SEARCH

- MIN_FILTER

- MIN_HESSIAN_SHIFT

- N_BCH_HISTORY

## Keyword descriptions

FILTER_FACTOR: real = 1.00000000E+000

  Usage: FILTER_FACTOR 10.0

  Allows to set a separate EPS_FILTER in the newton iterations. The new EPS is EPS_FILTER*FILTER_FACTOR. [Edit on GitHub]

FILTER_FACTOR_SCALE: real = 1.00000000E+000

  Usage: FILTER_FACTOR_SCALE 0.5

  Allows for dynamic EPS_FILTER. Updates the filter factor every SCF-Newton step by FILTER_FACTOR=FILTER_FACTOR*FILTER_FACTOR_SCALE [Edit on GitHub]

LINE_SEARCH: enum = 3POINT

  Usage: LINE_SEARCH 3POINT

  Valid values:

  - `3POINT` Performs a three point line search

  - `3POINT_2D` Only for spin unrestricted calcualtions. Separate step sizes for alpha and beta spin using a fit to a 2D parabolic function

  Line serch type used in the curvy_setp optimization. [Edit on GitHub]

MIN_FILTER: real = 1.00000000E+000

  Usage: MIN_FILTER 1.0

  Lowest EPS_FILTER in dynamic filtering. Given as multiple of EPS_FILTER: EPS_FILTER_MIN=EPS_FILTER*MIN_FILTER [Edit on GitHub]

MIN_HESSIAN_SHIFT: real = 0.00000000E+000

  Usage: MIN_HESSIAN_SHIFT 0.0

  Minimal eigenvalue shift for the Hessian in the Newton iteration. Useful for small band gap systems (0.5-1.0 recommended). [Edit on GitHub]

N_BCH_HISTORY: integer = 7

  Usage: N_BCH_HISTORY 5

  Number of stored matrices in the Baker-Campbell-Hausdorff series. Reduces the BCH evaluation during line search but can be memory intense. [Edit on GitHub]