ODDONLY: Difference between revisions

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Description: {{TAG|ODDONLY}}=.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> odd.
Description: {{TAG|ODDONLY}}=.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> odd.
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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


:<math>
:<math>
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{{TAG|ODDONLY}}=.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> odd. 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|ODDONLY}}=.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> odd. 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|EVENONLY}},
{{TAG|EVENONLY}},
[[Hartree-Fock_and_HF/DFT_hybrid_functionals#downsampling|downsampling]],
[[Downsampling of the Hartree-Fock operator|downsampling]]
[[Hartree-Fock_and_HF/DFT_hybrid_functionals]]


{{sc|ODDONLY|Examples|Examples that use this tag}}
{{sc|ODDONLY|Examples|Examples that use this tag}}
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[[Category:INCAR]][[Category:XC Functionals]][[Category:Hybrids]][[Category:Many-Body Perturbation Theory]]
[[Category:INCAR tag]][[Category:Exchange-correlation functionals]][[Category:Hybrid_functionals]][[Category:Many-body perturbation theory]][[Category:GW]]

Latest revision as of 12:04, 18 October 2023

ODDONLY = .TRUE. | .FALSE.
Default: ODDONLY = .FALSE. 

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


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.

ODDONLY=.TRUE. selects a subset of k-points with C1=C2=C3=1, and n1+n2+n3 odd. 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, EVENONLY, downsampling

Examples that use this tag