[Wien] Q:How many k-points are appropriate in a calculation on supercell

[Jiang Jun]

Dear Stefaan:
Thank you greatly for your warmly reply!
In fact,I chose the k-mesh size and basis set after TEST for my special 
system. My statement is not rigorous.

If I mesh 56 k-points in the IBZ of a small cell,only 7 points (with the same 
RKmax) is needed for the IBZ of a supercell cell.

That is a good news for me!

Thank you again!

Jun Jiang 
> >Usually, I chose 1000-3000 k-points in a unit cell with RminKmax=7.00.
> >
> >  
> >
> Such a statement is dangerous. k-mesh size and basis set size must
> always be TESTED. There are no safe default values. With a choice as you
> state it, you might sometimes be using unneccessary computer resources,
> or (worse) sometimes be producing uncorrect results.
> 
> >It takes too much time,if I still keep 3000 k-points in the SCF.
> >
> >How many k-points are appropriate when dealing with a 2*2*2 supercell?
> >Is it feasible to choose 300 k-points or decrease the value of RminKmax to 
> >6.00?
> >  
> >
> First test the k-mesh (and RKmax) for the small cell. A 2x2x2 cell is 8
> times larger, hence the IBZ is 8 times smaller. A k-mesh of the same
> quality as for you small cell contains 8 times *less* points in the IBZ
> for your supercell.
> 
> Stefaan
> 
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