This variable controls how much filter preconditioner is applied. A value of 1.0 means no preconditioning, 0.5 is the standard.
The default is 0.5, except for periodic systems where the default is 0.6.
If you observe that the first eigenvectors are not converging properly, especially for periodic systems, you should increment this value.
The allowed range for this parameter is between 0.5 and 1.0.
For other values, the SCF may converge to wrong results.
call parse_variable(namespace, 'PreconditionerFilterFactor', default_alpha, alpha)