Keyword MIXING

This keyword controls the charge density mixing.
Options:

	$+<$Real$>$		Fixed charge density mixing parameter between 0 and 1.
	$-<$Real$>$		Dynamic charge density mixing parameter. The default is -0.3.
	OMA		The optimal mixing algorithm is activated.

Description:
With the charge density mixing parameter, Hartree damping [189] (also called Pratt or linear mixing) of the charge density fitting coefficients is performed. The smaller the mixing parameter, the larger is the damping. For some systems, a very small mixing parameter (0.1) may be necessary. If a dynamic mixing parameter is chosen, the parameter is reduced during the SCF iterations if the MinMax SCF error increases. With the OMA option, the optimal mixing algorithm from Cancés [190] is activated. This option is recommended if the dynamical mixing fails or is slow to converge. It should be noted that use of OMA adds considerable overhead and that the method exhibits bad convergence for the case of small HOMO-LUMO gaps.