This keyword controls the charge density mixing.
Fixed charge density mixing parameter between 0 and 1.
Dynamic charge density mixing parameter. The default is -0.3.
The optimal mixing algorithm is activated.
With the charge density mixing parameter, Hartree damping  (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
 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