ecutprec -preconditioning energy cutoff
DESCRIPTION
The ecutprec variable determines the energy cutoff used for preconditioning of the electronic energy minimization. The value of ecutprec is used only if wf_dyn is set to PSD, PSDA or PSD_E and is ignored otherwise. The value of ecutprec must be given in Rydberg units, and must not exceed the value of ecut. A value of 0 (the default) corresponds to no preconditioning. The efficiency and stability of preconditioning varies depending on the details of the system under study. Small values of ecutprec (< ecut/2) usually improves convergence, but can result in instabilities in the electronic energy minimization. Preconditioning is useful when ecut is large (>20 Ry). The best value of ecutprec for a given system must be determined by experimenting.
DEFAULT VALUE
0
ALLOWED VALUES
[0,ecut]
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