NKREDZ: Difference between revisions

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In case one sets {{TAG|NKRED}}, the grid reduction factors will be uniformly set to ''C''<sub> 1</sub>=''C''<sub> 2</sub>=''C''<sub> 3</sub>={{TAG|NKRED}}. If one wants to specify separate grid reduction factors for ''C''<sub> 1</sub>, ''C''<sub> 2</sub>, and ''C''<sub> 3</sub> one should use ''C''<sub> 1</sub>={{TAG|NKREDX}}, ''C''<sub> 2</sub>={{TAG|NKREDY}}, and ''C''<sub> 3</sub>={{TAG|NKREDZ}}, respectively.
In case one sets {{TAG|NKRED}}, the grid reduction factors will be uniformly set to ''C''<sub> 1</sub>=''C''<sub> 2</sub>=''C''<sub> 3</sub>={{TAG|NKRED}}. If one wants to specify separate grid reduction factors for ''C''<sub> 1</sub>, ''C''<sub> 2</sub>, and ''C''<sub> 3</sub> one should use ''C''<sub> 1</sub>={{TAG|NKREDX}}, ''C''<sub> 2</sub>={{TAG|NKREDY}}, and ''C''<sub> 3</sub>={{TAG|NKREDZ}}, respectively.
'''Mind''': [[Hartree-Fock_and_HF/DFT_hybrid_functionals#downsamplingCaveat|there are circumstances under which '''NKRED''' and '''NKREDX''','''Y''','''Z''' should not be used!]]


== Related Tags and Sections ==
== Related Tags and Sections ==

Revision as of 16:59, 15 February 2011

NKREDZ = [integer]
Default: NKREDZ = 1 

Description: NKREDZ specifies a reduction factor for the q-point grid representation of the exact exchange potential along reciprocal space direction b 3.


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 (N 1×N 2×N 3) k-point set, {k}, for which the following holds

where b1,2,3 are the reciprocal lattice vectors of the primitive cell, and C i is the integer grid reduction factor along reciprocal lattice direction b i. This leads to a reduction in the computational workload by a factor:

In case one sets NKRED, the grid reduction factors will be uniformly set to C 1=C 2=C 3=NKRED. If one wants to specify separate grid reduction factors for C 1, C 2, and C 3 one should use C 1=NKREDX, C 2=NKREDY, and C 3=NKREDZ, respectively.

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

Related Tags and Sections

NKRED, NKREDX, NKREDY, EVENONLY, ODDONLY, downsampling, Hartree-Fock_and_HF/DFT_hybrid_functionals


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