[Pw_forum] D3.x limited to Gamma point?

[Badescu, Stefan]

Greetings,



I am trying to understand a detail of the D3 suite. Some literature suggests that it can be used to calculate the decay of phonons at any q-point. Looking at the code and at the inpt required by d3.x though, my first interpretation is that it works for Gamma phonon decaying through a q,-q channel.



In the calculation of force constant derivatives, the d3.x program requires

the perturbed densities at q0=0 and at the q of the decay channel, producing V^(3)(0,q,-q) .

To calculate V^(3)(k,q,k-q), does it make any sense to input fildrho given by a calculation at q, and  fild0rho given by a calculation at k? The calculation seems to work but I am not sure whether it is meaningful, i.e., whether this can be used to calculate the decay of a k-point phonon through q and a k-q phonons.



Thank you for any hint.

--Stefan
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