Dear Quantum Espresso users,
I'm attempting some basic
calculations in order to obtain the IR spectra of molecules. I did a
test for SiH4 molecule using the example given by Paolo in
http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_advph.html.
On the other hand, I tried to do the same kind of simulation but now
centering the molecule at the center of a simple cubic lattice.
I saw
that centering the molecule at the center of the lattice I obtained some
imaginary frequencies, 6 normal modes that are zero and positive
frequencies (It's attached the file).
I was wondering if I have to use
the transformation matrix in order to obtain the cartesian coordinates
(with the center of mass of the molecule at the origin of the cell) into
crystallographic units taking into account the symmetry of the lattice.
My question is, how is the way to define a molecule in order to obtain
the correct results?
I know that centering the molecule at the center
of the lattice is wrong due to the symmetry (C1).
Thanks in advance
Regards
--
Rubén Soria Martinez
PhD Student
Insitut de Physique et
Chimie des Matériaux de Strasbourg (IPCMS).
23 Rue du Loess
STRASBOURG
67034 France
TEL: +33 (0) 769289329s
Program DYNMAT v.6.1 (svn rev. 13369) starts on 18Dec2017 at 12:30: 8
This program is part of the open-source Quantum ESPRESSO suite
for quantum simulation of materials; please cite
"P. Giannozzi et al., J. Phys.:Condens. Matter 21 395502 (2009);
URL http://www.quantum-espresso.org";,
in publications or presentations arising from this work. More details at
http://www.quantum-espresso.org/quote
Parallel version (MPI), running on 8 processors
R & G space division: proc/nbgrp/npool/nimage = 8
Reading Dynamical Matrix from file sih4-3.dyn
...Force constants read
...epsilon and Z* read
Acoustic Sum Rule: || Z*(ASR) - Z*(orig)|| = 3.520865E-02
Acoustic Sum Rule: ||dyn(ASR) - dyn(orig)||= 6.199728E-01
A direction for q was not specified:TO-LO splitting will be absent
Polarizability (A^3 units)
multiply by 0.847578 for Clausius-Mossotti correction
4.038395 -0.007682 -0.013792
-0.007682 4.011199 0.003539
-0.013792 0.003539 4.025874
IR activities are in (D/A)^2/amu units
# mode [cm-1] [THz] IR
1 -1841.07 -55.1938 4.2824
2 -1837.21 -55.0783 4.1563
3 -1829.44 -54.8453 4.1729
4 -1562.99 -46.8574 0.0009
5 -1557.89 -46.7044 0.0019
6 -0.00 -0.0000 0.0000
7 -0.00 -0.0000 0.0000
8 -0.00 -0.0000 0.0000
9 0.00 0.0000 0.0000
10 0.00 0.0000 0.0000
11 0.00 0.0000 0.0000
12 4965.45 148.8603 0.0039
13 5024.85 150.6411 1.2028
14 5026.96 150.7045 1.1602
15 5028.58 150.7529 1.1763
DYNMAT : 0.01s CPU 0.01s WALL
This run was terminated on: 12:30: 8 18Dec2017
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JOB DONE.
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