EDIFF
EDIFF = [real]
Default: EDIFF = [math]\displaystyle{ 10^{-4} }[/math]
Description: EDIFF specifies the global break condition for the electronic SC-loop. EDIFF is specified in units of eV.
The relaxation of the electronic degrees of freedom stops if the total (free) energy change and the band-structure-energy change ('change of eigenvalues') between two steps are both smaller than EDIFF (in eV). For EDIFF=0, strictly NELM electronic self-consistency steps will be performed.
| Mind: In most cases, the convergence speed is exponential, so often, the cost for the few additional iterations is small. For high precision calculations, we recommend decreasing EDIFF to 1E-6. For finite difference calculations (e.g. phonons), even EDIFF = 1E-7 might be required in order to obtain very accurate results. |