ISMEAR

ISMEAR = -5 | -4 | -3 | -2 | -1 | 0 | [integer]>0
Default: ISMEAR = 1 

Description: ISMEAR determines how the partial occupancies f_nk are set for each orbital. SIGMA determines the width of the smearing in eV.

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• ISMEAR=N (N>0): method of Methfessel-Paxton order N.

Mind: For the Methfessel-Paxton scheme the partial occupancies can be negative.

• ISMEAR=0: Gaussian smearing.
• ISMEAR=−1: Fermi smearing.
• ISMEAR=−2: partial occupancies are read in from the WAVECAR or INCAR file, and kept fixed throughout run.

To set the occupancies specify

 FERWE = f1 f2 f3 ... f(NBANDS)

and for spin-polarized calculations, additionally

 FERDO = f1 f2 f3 ... f(NBANDS)

in the INCAR file. The (partial) occupancies must be specified for all bands and k-points. The band-index runs fastest. The occupancies must be between 0 and 1 (for spin-polarized and non-spin-polarized calculations).

Mind: Partial occupancies are also written to the OUTCAR file, but in this case they are multiplied by 2, i.e. they are between 0 and 2.

• ISMEAR=−3: perform a loop over smearing-parameters supplied in the INCAR file.

In this case a tag

 SMEARINGS= ismear1 sigma1  ismear2 sigma2  ...

must be present in the INCAR file, supplying different smearing parameters. IBRION has to be set to -1 and NSW to the number of supplied pairs ismear_i/sigma_i. The first loop is done using the tetrahedron method with Blöchl corrections.

• ISMEAR=−4: tetrahedron method (use a Γ-centered k-mesh).
• ISMEAR=−5: tetrahedron method with Blöchl corrections (use a Γ-centered k-mesh).

Related Tags and Sections

SIGMA

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