CheFSI input documentation
==========================

Initialize with stopping criteria and filter order.


Used to initialize class :class:`qimpy.dft.electrons.CheFSI`.

YAML template:
--------------

.. parsed-literal::

   :yamlparam:`qimpy.dft.electrons.CheFSI:n-iterations`: 100     :yamlcomment:`# Number of diagonalization iterations.`
   :yamlparam:`qimpy.dft.electrons.CheFSI:eig-threshold`: 1e-08  :yamlcomment:`# Convergence threshold on eigenvalues in Hartrees.`
   :yamlparam:`qimpy.dft.electrons.CheFSI:filter-order`: 10      :yamlcomment:`# Order of the Chebyshev filter.`
   :yamlparam:`qimpy.dft.electrons.CheFSI:init-threshold`: 0.1   :yamlcomment:`# Eigenvalue threshold for initial Davidson steps.`

Parameters:
-----------

n-iterations
++++++++++++

*Type:* :yamltype:`int`, *Default:*  100

Number of diagonalization iterations.
This only affects fixed-Hamiltonian calculations because the
self-consistent field method overrides this when diagonalizing
in an inner loop.

eig-threshold
+++++++++++++

*Type:* :yamltype:`float`, *Default:*  1e-08

Convergence threshold on eigenvalues in Hartrees.
Stop when the maximum change in any eigenvalue between iterations
falls below this threshold. This only affects fixed-Hamiltonian
calculations because the self-consistent field method overrides
this when diagonalizing in an inner loop.

filter-order
++++++++++++

*Type:* :yamltype:`int`, *Default:*  10

Order of the Chebyshev filter.
This amounts to the number of Hamiltonian evaluations per band
per eigenvalue iteration.

init-threshold
++++++++++++++

*Type:* :yamltype:`float`, *Default:*  0.1

Eigenvalue threshold for initial Davidson steps.
This controls the accuracy of a coarse Davidson diagonalization
that creates a reasonable starting point for CheFSI.