The mixing_parameter variable determines the initialization of the inverse of the Hessian matrix. A small mixing parameter will lead to smaller movements of the charge density during the first few iterationss. Later, when the inverse of the Hessian matrix has been constructed, the mixing parameter does not change the algorithm much.
mixing_parameter 0.33 initialize H to 0.33 of standard size
Default: mixing_parameter 0.77
For smaller wave vectors, a Broyden type mixing is used, for larger wave numbers a linear mixing is employed. The energy cutoff for this Broyden mixing may be set with the parameter:
mixing_energy_cutoff 5.0 Sets Broyden mixing cutoff to 5.0Ry
Often a small fraction of the total cutoff is sufficient, say 5 Ry.
Default: 5 Ry