[Pw_forum] gamma phonongs for alloys

[Sophia Nishad]

Hi,

I wanted to know what is the best approch to compute gamma phonons for
alloys with the linear response thoery.

To include disorder effects how large the supercell has to be for a model
alloy say, SiGe. Would the result converge for a supercell of 64 atoms? or
more atoms are needed. Would it be efficient to use mass approximation or
any other tricks like VCA approximation for the pseudopotential?

Also, how about any related properties like strain-shift coefficents. Would
they be sensitive to size of supercell as well?

Thanks in advance,
-- 
Sophia
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