My Community

Hello,

When I run the following calculation, I observe that the bottom two layers move drastically (which they shouldn't as per selective dynamics tag). The resulting "optimized geometry" is something ridiculous in which the Cu atoms in the bottom two layers move ~10 angstroms apart. I would really appreciate it if someone could tell if me there is something inherently wrong with this POSCAR/INCAR?

POSCAR:
CuBSlab
5.12
1.00 0.00 0.00
0.00 1.00 0.00
0.00 0.00 5.00
12 2
Selective Dynamics
Cartesian
0.00 0.00 0.00 F F F
2.56 0.00 0.00 F F F
0.00 2.56 0.00 F F F
2.56 2.56 0.00 F F F
0.00 0.00 2.56 F F F
2.56 0.00 2.56 F F F
0.00 2.56 2.56 F F F
2.56 2.56 2.56 F F F
0.00 0.00 5.12 T T T
2.56 0.00 5.12 T T T
0.00 2.56 5.12 T T T
2.56 2.56 5.12 T T T
1.28 1.28 5.12 T T T
3.84 3.84 5.12 T T T

INCAR:

general:

ISTART = 0

ICHARGE = 2

SYSTEM = CuBSlab

ENCUT = 450

ISMEAR = 1

SIGMA = 0.2

ISPIN = 2

GGA = RP

LREAL = FALSE

EDIFF = 1e-5


dynamic:

NSW = 150

IBRION = 1

POTIM = 0.5

Thanks!

Please ensure that you do not have a space between the beginning of the line with "Selective dynamics" and the letter "S". "S" have to be the first character in the line. Otherwise the Selective dynamics command won't work.

please also make sure that you do not mix up carthesian coordinates (your POSCAR) and direct coordinates (always written in CONTCAR)

I changes the poscar file to direct coordinates and that seemed to fix the problem.

Thank you for telling me I needed to write.
Selective Dynamics with S as first Character in line instead of space or tab. I spent an hour messing around with the Poscar until I found this.