Used by the Chebyshev filter only. The degree of the Chebyshev polynomial used to dampen the interval of eigenstates one is not interested in. If used in conjunction with "OptimizeChebyshevFilterDegree", which is the default, "ChebyshevFilterDegree" defines the the maximum Chebyshev polynomial degree Octopus will consider when determining an approximate, optimal degree.
If not used in conjunction with "OptimizeChebyshevFilterDegree", this defines the polynomial degree used for all SCF steps.
The larger the degree, the larger the separation between the subspaces, which will reduce the number of SCF iterations
required to reach convergence. However, ChebyshevFilterDegree also directly correlates with the number of matrix-vector
products performed on the Hamiltonian per SCF step, and so larger values result in slower SCF cycles.
A value in the range 8 <= ChebyshevFilterDegree <= 20 is reasonable.
call parse_variable(namespace, 'ChebyshevFilterDegree', default_chebyshev_params%degree, eigens%cheby_params%degree)