In the WMD github group, the vasp file of CH3NH3PbI3 have the P1 symmetry and lattice parameters are a= 6.28,b=6.228,c=6.37 angstroms. When I calculate the mechanical properties the values are more than the values in research papers,around ~2.5 times of it.
What should I do to rectify those parameters right as well as what should I use as input in vc-relax,scf calculations and thermo_control file?