Unit cell parameters were taken from the phonopy example folder. Silicon unit cell contains 8 atoms, thus 24 frequencies (phonons), three acoustic close to zero.
For this example vasp_raman.py script version [0.5.1] (https://raw.github.com/raman-sc/VASP/3cb3cdf0682609365c4b966472ef6eb5be1defc5/vasp_raman.py) was used.
Raman intensities for all modes will be computed in one go. For the multi-step procedure see Cyclopentadiene example.
Working directory should contain the following files (FAT file system has different soft linking ways):
INCAR - should contain LEPSILON=.TRUE. or LCALCEPS=.TRUE. because we want 'MACROSCOPIC STATIC DIELECTRIC TENSOR' in the OUTCAR
KPOINTS - just kpoints (soft link of the KPOINTS file from the PHONON folder, to prevent errors)
OUTCAR.phon - should contain 'Eigenvectors after division by SQRT(mass)' either from VASP (soft link of the OUTCAR file from the PHONON folder)
POSCAR.phon - VASP5 format is *required* (atomic symbols and numbers), at this point only positive scales are supported (soft link of the POSCAR file from the PHONON folder)
POTCAR - `PAW_PBE Si 05Jan2001` PP (soft link to the POTCAR file from the PHONON folder)
raman.sub - shell script for the scheduler to *do the deed*
Contents of the raman.sub:
#!/bin/bash
#PBS -A ONRDC17403171
#PBS -l select=5:ncpus=32:mpiprocs=32
#PBS -l walltime=01:00:00
#PBS -q debug
#PBS -j oe
#PBS -N Si_bulk-R
#PBS -V
cd $PBS_O_WORKDIR
ulimit -s unlimited # remove limit on stack size
export VASP_RAMAN_RUN='aprun -B /u/afonari/vasp.5.3.2/vasp.5.3/vasp &> job.out'
export VASP_RAMAN_PARAMS='01_21_2_0.01'
python /u/afonari/vasp_raman.py > vasp_raman.out
Submit all calculations to the scheduler:
qsub raman.sub
After the job finished, a lot of OUTCAR files have been created (strictly speaking 42... the answer??!), vasp_raman.dat will contain Raman activities for the future processing (for example with gnuplot).
From experiment, Raman spectrum of the bulk silicon contains only one intense peak at around 520 cm-1 (J.H. Parker, et al., Phys Rev, 155, 712 (1967)), vasp_raman.dat contains:
# mode freq(cm-1) alpha beta2 activity
1 504.47552 0.0000409 780.7952797 5465.5669580
2 504.47464 0.0045779 779.0264832 5453.1863253
3 504.47201 -0.0031882 779.4324411 5456.0275454
4 447.84208 0.0006131 0.0005437 0.0038231
5 447.84107 -0.0017167 0.0000277 0.0003268
6 447.84076 0.0049049 0.0000643 0.0015326
7 447.83928 0.0004905 0.0001417 0.0010030
8 447.83865 -0.0380539 0.0203246 0.2074370
9 447.82907 -0.0295112 0.0906046 0.6734232
10 402.16258 -0.0002044 0.0001276 0.0008950
11 402.16054 0.0001226 0.0000161 0.0001131
12 402.15924 -0.0008992 0.0000119 0.0001199
13 402.15921 -0.0012262 0.0000106 0.0001422
14 402.15746 0.0008584 0.0002334 0.0016672
15 402.15492 0.0005722 0.0000023 0.0000306
16 145.82303 0.0002044 0.0000004 0.0000045
17 145.82113 -0.0000817 0.0000001 0.0000010
18 145.81855 -0.0002044 0.0000002 0.0000029
19 145.81681 -0.0001226 0.0000007 0.0000054
20 145.81480 0.0000817 0.0000004 0.0000029
21 145.81429 0.0000409 0.0000002 0.0000011
Triple degenerate mode at 504 cm-1 has the largest intensity.
Shannon Stauffer (UT Austin, PI: G. Henkelman): Email.
Alexandr Fonari (Georgia Tech, PIs: J.-L. Bredas/V. Coropceanu): Email