EVENONLY: Difference between revisions

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{{TAGDEF|EVENONLY|.TRUE.|.FALSE.|.FALSE.}}
{{TAGDEF|EVENONLY|.TRUE. {{!}} .FALSE.|.FALSE.}}


Description: {{TAG|EVENONLY}}=.TRUE. selects a subset of '''k'''-points for the representation of the Fock exchange potential, with ''C''<sub>1</sub>=''C''<sub>2</sub>=''C''<sub>3</sub>=1, and ''n''<sub>1</sub>+''n''<sub>2</sub>+''n''<sub>3</sub> even.
Description: {{TAG|EVENONLY}}=.TRUE. selects a subset of '''k'''-points for the representation of the Fock exchange potential, with ''C''<sub>1</sub>=''C''<sub>2</sub>=''C''<sub>3</sub>=1, and ''n''<sub>1</sub>+''n''<sub>2</sub>+''n''<sub>3</sub> even.
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One may restrict the sum over '''q''' in the [[Hartree-Fock_and_HF/DFT_hybrid_functionals#VxFock|Fock exchange potential]] (or one of its [[Hartree-Fock_and_HF/DFT_hybrid_functionals#VxFockSR|short range counterparts]]) to a subset, {'''q'''<sub>'''k'''</sub>}, of the full (''N''<sub>1</sub>&times;''N''<sub>2</sub>&times;''N''<sub>3</sub>)  '''k'''-point set, {'''k'''}, for which the following holds
One may restrict the sum over '''q''' in the [[Hybrid functionals: formalism|Fock exchange potential]] (or one of its short range counterparts) to a subset, {'''q'''<sub>'''k'''</sub>}, of the full (''N''<sub>1</sub>&times;''N''<sub>2</sub>&times;''N''<sub>3</sub>)  '''k'''-point set, {'''k'''}, for which the following holds


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{{TAG|EVENONLY}}=.TRUE. selects a subset of '''k'''-points with ''C''<sub>1</sub>=''C''<sub>2</sub>=''C''<sub>3</sub>=1, and ''n''<sub>1</sub>+''n''<sub>2</sub>+''n''<sub>3</sub> even. It reduces the computational work load for HF type calculations by a factor two, but is only sensible for high symmetry cases (such as sc, fcc or bcc cells).
{{TAG|EVENONLY}}=.TRUE. selects a subset of '''k'''-points with ''C''<sub>1</sub>=''C''<sub>2</sub>=''C''<sub>3</sub>=1, and ''n''<sub>1</sub>+''n''<sub>2</sub>+''n''<sub>3</sub> even. It reduces the computational work load for HF type calculations by a factor two, but is only sensible for high symmetry cases (such as sc, fcc or bcc cells).


'''Mind''': [[Hartree-Fock_and_HF/DFT_hybrid_functionals#downsamplingCaveat|there are circumstances under which downsampling should not be used!]]
{{NB|warning|[[Downsampling_of_the_Hartree-Fock_operator#Caveat: when one should not use downsampling|there are circumstances under which '''NKRED''' and '''NKREDX''','''Y''','''Z''' should not be used!]]}}


== Related Tags and Sections ==
== Related tags and articles ==
{{TAG|NKRED}},
{{TAG|NKRED}},
{{TAG|NKREDX}},
{{TAG|NKREDX}},
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{{TAG|NKREDZ}},
{{TAG|NKREDZ}},
{{TAG|ODDONLY}},
{{TAG|ODDONLY}},
[[Hartree-Fock_and_HF/DFT_hybrid_functionals#downsampling|downsampling]],
[[Downsampling of the Hartree-Fock operator|downsampling]]
[[Hartree-Fock_and_HF/DFT_hybrid_functionals]]
 
{{sc|EVENONLY|Examples|Examples that use this tag}}
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[[The_VASP_Manual|Contents]]


[[Category:INCAR]][[Category:Hybrids]]
[[Category:INCAR tag]][[Category:Exchange-correlation functionals]][[Category:Hybrid_functionals]]

Latest revision as of 12:04, 18 October 2023

EVENONLY = .TRUE. | .FALSE.
Default: EVENONLY = .FALSE. 

Description: EVENONLY=.TRUE. selects a subset of k-points for the representation of the Fock exchange potential, with C1=C2=C3=1, and n1+n2+n3 even.


One may restrict the sum over q in the Fock exchange potential (or one of its short range counterparts) to a subset, {qk}, of the full (N1×N2×N3) k-point set, {k}, for which the following holds

where b1,2,3 are the reciprocal lattice vectors of the primitive cell, and Ci is the integer grid reduction factor along reciprocal lattice direction bi.

EVENONLY=.TRUE. selects a subset of k-points with C1=C2=C3=1, and n1+n2+n3 even. It reduces the computational work load for HF type calculations by a factor two, but is only sensible for high symmetry cases (such as sc, fcc or bcc cells).


Warning: there are circumstances under which NKRED and NKREDX,Y,Z should not be used!

Related tags and articles

NKRED, NKREDX, NKREDY, NKREDZ, ODDONLY, downsampling

Examples that use this tag