[Pw_forum] force constants file
Bartek Wiendlocha
bwiendlocha at interia.pl
Mon Apr 11 13:23:38 CEST 2005
Hello,
Could Anyone help me and write a (detailed..) description of the force
constants file, generated with q2r (usually *.fc)?
for ex.: (metallic system)
------------
2 3 4 5.6370000 0.0000000 1.0870000 0.0000000 0.0000000
0.0000000 --> lattice
1 'Al ' -> atoms 24588.6885119930 -> ??
2 'B ' -> atoms 9851.88001536857 -> ??
1 1 0.0000000 0.0000000 0.0000000 -> positions
2 2 0.5000000 0.2886751 0.5435000
3 2 0.0000000 0.5773503 0.5435000
F
8 8 8 -> grid size
1 1 1 1 --> ??
1 1 1 --> ?? 1.56778730300E-01 --> force constant, but for which
atoms?
2 1 1 -2.70214755142E-02
.....etc...
-----------------
are the force constants divided by mass ? How to find the distance in
real space (or the number of nearest neighbours) up to which the FC are
calculated?
I need these information to calculate the inverse force constant matrix
(I think so..).
Thanks for help,
Bartek
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