I am learning how to calculate piezoelectric tensors with vasp, taking BaTiO3 (mp-5777) as a base. According to my calculations the tensor is [[-0. , -0. , -0. , -0.42231, -0. , -0. ],

[ 0.91759, 3.04261, 2.30926, -0. , 0. , 0. ],

[ 0. , 0. , 0. , -0. , 1.41856, -0. ]], but in materials project the result is [[-0. , -0. , -0. , 0, -0. , 1.302 ],

[ −2.244, −3.437, −0.6925, 0. , 0. , 0. ],

[ 0. , 0. , 0. , -0. , 0, -0. ]]. My incar after relaxation is:

ALGO = Normal

EDIFF = 1E-7

ENCUT = 520.0

IBRION = -1

ISIF = 2

ISMEAR = -5

ISPIN = 2

LASPH = True

LMAXMIX = 4

LORBIT = 11

LREAL = .False.

LWAVE = False

MAGMOM = 10*0.6

NELM = 200

NSW = 0

PREC = Accurate

SIGMA = 0.05

LCHARG = .TRUE.

LEPSILON = .TRUE.

IBRION = 6

Any suggestions as to why these differences occur?