Thank you Andrea I think the phonon calculated with 13 dynamical matrices is wrong because when I calculate the anisotropic coefficients of thermal expansion in zirconium I do PW calculations as well as phonon calculations in several lattice parameters. In some of them (not in all of them), QE calculate 13 dynamical matrices and in the other 12. When I use this data to calculate the anisotropic coefficient of thermal expansion I got very strange results that do not agree with some publications which also calculate it from DFT. I do not know what is the problem. Maybe there is some problem in q2r.x. Using nr1=30, nr2=30, nr3=48 indeed solve the problem. In addition, different ecut and ecutrho also solve the problem. I now calculate the coefficient of anisotropic thermal expansion in zirconium again with ecut=50 and ecutrho=250. These calculations always produce 12 dynamical matrices. These calculations takes a few days on my machines. When I will get the results I will report if it makes any difference. Uri Argaman Ben-Gurion University Israel
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