Beyond these major factors, there is still room for some adjustment. The needed planewave basis set will depend on the pseudopotential (or PAW atomic dataset) that is used. Some might be softer than others and need a smaller planewave basis set. They might possibly be less accurate as well ...
If one is only interested in ground-state properties and forces, one might also get some speed up by using a real-space representation of density and potential on a real space FFT grid that does not allow their fine details to be taken into account (actually, filtering such quantities). This is achieved by lowering boxcutmin below its theoretically needed value of 2.0 .
The choice of the FFT algorithm implementation, see fftalg might also lead to significant speed up, on specific machines.
For specific k-points, time-reversal symmetry can be used to represent the wavefunctions with their real part, instead of both their real and complex parts. This allows halving the memory needs, as well as the CPU time. See istwfk.
Other input variables related to tuning the speed or the memory usage are for expert users only.
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Basic input variables:
... boxcutmin [BOX CUT-off MINimum]
... istwfk [Integer for choice of STorage of WaveFunction at each k point]
Useful input variables:
... fftalg [Fast Fourier Transform ALGorithm]
Input variables for experts:
... exchn2n3d [EXCHange N2 and N3 Dimensions]
... extrapwf [flag - EXTRAPolation of the Wave-Functions]
... fftcache [Fast Fourier Transform CACHE size]
... iboxcut [Integer governing the internal use of BOXCUT - not a very good choice of variable name]
... nbdblock [Number of BanDs in a BLOCK]
... nloc_alg [Non LOCal ALGorithm]
... nloc_mem [Non LOCal MEMOry]
... ortalg [ORThogonalisation ALGorithm]
... useylm [USE YLM (the spherical harmonics)]
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tests/v3/Input: t43.in
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