Since the KS propagator is non-linear, each propagation step should be performed self-consistently. In practice, for most purposes this is not necessary, except perhaps in the first iterations. This variable holds the number of propagation steps for which the propagation is done self-consistently.
The self consistency has to be measured against some accuracy
threshold. This variable controls the value of that threshold.
td/propagator_elec.F90 : 380
call parse_variable(namespace, 'TDSCFThreshold', CNST(1.0e-6), tr%scf_threshold)