I have a DFPT job (IBRION=8) run on VASP with the Virtual Crystal Approximation (VCA) method turned on. The system is 80at.% Ti, 20at.% V. INCAR and vasprun (files attached). Typically I use PHONOPY to process the output using
phonopy --fc vasprun.xml
However, with the VCA turned on, it looks like some of the dynmat hessian elements (specifically, it looks like only the diagonal elements, but I could be wrong) are reported as ********
Of course, I'd be happy to provide any other job files/details that may be important here. Any help in understanding and/or fixing this would be greatly appreciated.
Thanks