UT theoretical chemistry code forum

Hello,

I would like to use the DynMat code to calculate harmonic frequencies by finite differences (I cannot use IBRION=5 because the calculation takes longer than the maximum wall time of my jobs).

I read the manual here: https://theory.cm.utexas.edu/vtsttools/dymmat.html
Then I tried a test calculation for a CO2 molecule, so I have a POSCAR file with 3 atoms, I set NSW=10 (3*3 +1) in the INCAR file, and I use a DISPLACECAR file with a 3x3 matrix filled with the number 0.02 (the displacement in Ångström).

However, when I try to run it, it only calculates displacements for the first atom in the POSCAR, so it ends after 4 ionic steps instead of 10 (one to calculate the forces of the initial geometry, and three for displacements of the C atom in each coordinate).

Maybe I am misunderstanding how to write the DISPLACECAR file? Please find attached INCAR, POSCAR, and DISPLACECAR, as well as the XDATCAR so you can see the displacements.

Thank you for your help.

Try changing the line:

EDIFF = -1E-20
to
EDIFFG = -1E-20

Hello Prof. Henkelman,

I had not noticed that typo in the INCAR. That was it, now it works fine. Thank you and sorry for the trouble.

Fantastic, happy to help!