How to completely avoid "aliasing errors"?

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byin
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How to completely avoid "aliasing errors"?

#1 Post by byin » Tue May 09, 2017 4:08 pm

Dear all,

I have some questions about the "aliasing errors". I have set PREC=accurate in INCAR, but there are still warnings in the OUTCAR. Why?

For example, in one job, I set PREC=accurate. The info written in OUTCAR is

dimension x,y,z NGX = 84 NGY = 80 NGZ = 210
dimension x,y,z NGXF= 168 NGYF= 160 NGZF= 420

I would recommend the setting:
dimension x,y,z NGX = 83 NGY = 79 NGZ = 208

The FFT grid with 83, 79, 208 is approximaly 2G_cut. So the actual values used in calculation 84, 80 and 210 have already exceeded the 2G_cut. But in the following there are two warnings

WARNING: aliasing errors must be expected set NGX to 86 to avoid them
WARNING: aliasing errors must be expected set NGY to 82 to avoid them

Can I ask why this warning happen?

Is there any parameters in INCAR which can guarantee to avoid "aliasing errors"? It seems that PREC=accurate is not enough.

Thanks!

Best,
Binglun

dscullion12
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Re: How to completely avoid "aliasing errors"?

#2 Post by dscullion12 » Sat May 13, 2017 2:07 pm

Dear Binglun,

You can set the values of NGX, NGY and NGZ by hand in the INCAR. I would recommend to do this if aliasing errors arise.

All the best,

Declan

byin
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Re: How to completely avoid "aliasing errors"?

#3 Post by byin » Fri Jun 02, 2017 1:23 pm

dscullion12 wrote:Dear Binglun,

You can set the values of NGX, NGY and NGZ by hand in the INCAR. I would recommend to do this if aliasing errors arise.

All the best,

Declan

Thanks Declan,
Yes, this is one way to solve this problem.
But it would be better if the some INCAR parameter can guarantee no aliasing errors from scratch.
Best,
Binglun

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