EDIFF: Difference between revisions
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{{TAGDEF|EDIFF|[real]|<math>10^{-4}</math>}} | {{TAGDEF|EDIFF|[real]|<math>10^{-4}</math>}} | ||
Description: {{TAG|EDIFF}} specifies the global break condition for the electronic SC-loop. | Description: {{TAG|EDIFF}} specifies the global break condition for the electronic SC-loop. EDIFF is specified in units of eV. | ||
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The relaxation of the electronic degrees of freedom will be stopped if the total (free) energy change and the band structure energy change ('change of eigenvalues') between two steps are both smaller than {{TAG|EDIFF}} (in eV). For {{TAG|EDIFF}}=0, {{TAG|NELM}} electronic SC-steps will | The relaxation of the electronic degrees of freedom will be stopped if the total (free) energy change and the band structure energy change ('change of eigenvalues') between two steps are both smaller than {{TAG|EDIFF}} (in eV). For {{TAG|EDIFF}}=0, strictly {{TAG|NELM}} electronic SC-steps will be performed. | ||
'''Mind''': In most cases the convergence speed is exponential. For high precision calculations we recommend to decrease {{TAG|EDIFF}} to 1E-6. For | '''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 to decrease {{TAG|EDIFF}} to 1E-6. For finite difference calculations (e.g. phonons), even {{TAG|EDIFF}} = 1E-7 might be required in order to obtain very accurate results. | ||
== Related Tags and Sections == | == Related Tags and Sections == | ||
Revision as of 12:53, 7 June 2021
EDIFF = [real]
Default: EDIFF =
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 will be stopped 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 SC-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 to decrease 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.