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ENCUT

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ENCUT = [real] 

Default: ENCUT = largest ENMAX on the POTCAR file

Description: ENCUT specifies the cutoff energy for the planewave basis set in eV.


All plane waves with a kinetic energy smaller than Ecut are included in the basis set, i.e.,

 | \mathbf{G} + \mathbf{k} | < G_{\mathrm{cut}} with  E_{\mathrm{cut}} = \frac{\hbar^2}{2m} G^2_{\mathrm{cut}}

The number of plane waves differs for each k-point, leading to a superior behaviour for, e.g. energy-volume calculations. If the volume is increased the total number of plane waves changes fairly smoothly. The criterion | \mathbf{G} | <   G_{\mathrm{cut}} (i.e. same basis set for each k-point) would lead to a very rough energy-volume curve and, generally, slower energy convergence.

The POTCAR files contain a default ENMAX (and ENMIN) line, therefore it is in principle not necessary to specify ENCUT in the INCAR file. For calculations with more than one species, the maximum cutoff ENMAX or ENMIN value is used for the calculation (see PREC). For consistency reasons we still recommend to specify the cutoff manually in the INCAR file and keep it constant throughout a set of calculations.

Related Tags and Sections

ENMAX, ENMIN, PREC, POTCAR, Precision


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