phonons: getting a low enough force
Posted: Tue Jul 30, 2013 10:57 pm
I am stumped on what to do about the following:
1. I relax a structure of say 20 atoms to < 1x10-6 Ha/bohr (tolmxf 1.0d-6)
2. I use this relaxed structures acell and xred as inputs to the beginning of a phonon calculation that
has tolvrs 10d-18 .
3. when I get the forces back after the completion of the tolvrs,
they are bigger than 1x10-6 ha/bohr -- sometimes by 1-2 orders of magnitude.
My questions:
1. why is this?
2. what can I do to improve the forces for the tolvrs part?
tnx,
jb
1. I relax a structure of say 20 atoms to < 1x10-6 Ha/bohr (tolmxf 1.0d-6)
2. I use this relaxed structures acell and xred as inputs to the beginning of a phonon calculation that
has tolvrs 10d-18 .
3. when I get the forces back after the completion of the tolvrs,
they are bigger than 1x10-6 ha/bohr -- sometimes by 1-2 orders of magnitude.
My questions:
1. why is this?
2. what can I do to improve the forces for the tolvrs part?
tnx,
jb