Hi, I am interested in looking at effects of using van der Waals functionals like vdW-DF2 on the phonon dispersion of organic crystals. Preliminary results indicate that there might be some issues with using DFPT and DF2 together. More specifically, DFPT gives a couple "very imaginary" frequencies (below -100cm^-1) for Gamma-point phonons (with and without acoustic sum rule), while finite displacement results seem to be just fine, using the same convergence parameters.
So before I dig deeper into eventual other issues at play here, I wanted to ask if you know of any incompatibilities when using DFPT and vdW-DF2? Either inherently embedded in the underlying theory (which I could then dig into first), or just in the way it is implemented in QE. Thanks for your help, Florian --- Florian Altvater PhD candidate UC Berkeley/LBNL _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
