Setting IBRION=8 or IBRION=7 selects the calculation of the interatomic force constants using density functional perturbation theory. For IBRION=8, symmetry is taken into account, whereas IBRION=7 neglects symmetry considerations and is thus usually significantly more expensive. If IBRION=7 (or IBRION=8) and LEPSILON=.TRUE. is selected, the relaxed-ion static dielectric tensor, or low frequency dielectric tensor, and the relaxed-ion piezoelectric tensors are determined [84]. All values are collected and printed at the end of the OUTCAR file (see also Sec. 6.21.7). Specifically the ionic contribution to the piezoelectric tensor is printed after
PIEZOELECTRIC TENSOR IONIC CONTR for field in x, y, z (C/m^2)and the ionic contributions to the dielectric tensor are printed after:
MACROSCOPIC STATIC DIELECTRIC TENSOR IONIC CONTRIBUTIONNote that LRPA=.FALSE. must be selected to obtain these values.