phonon spectrum for rhombohedral crystal
Posted: Tue Jan 17, 2012 7:53 am
Dear all,
I am trying to simulate Sb2Te3 phonon spectrum as described in tutorial rf2. As the calculations are quite time consuming for converged ecut, I used rhombohedral primary cell:
Then, how should I plot phonon spectrum in anaddb? In particular, anaddb help file said that brav=1 is for all lattices? Then, can I use it with my results for rhombohedral one? And what is the difference between brav=1 and brav=4, e.g. for hexagonal lattice, or brav=1 and brav=2 for FCC?
I am asking because I have plotted phonon spectrum for Si as an exercise. At first I calculate ddb using FCC cell and then plot phonon spectrum using brav=2 and brav=1 - they look similar but for brav=1 - curves look less smooth. But in general: is it correct at all?
Thank you,
dps
I am trying to simulate Sb2Te3 phonon spectrum as described in tutorial rf2. As the calculations are quite time consuming for converged ecut, I used rhombohedral primary cell:
Code: Select all
#Definition of the unit cell
#from previous cell optimization
acell 1.6656138762E+01 1.6656138762E+01 1.6656138762E+01
rprim 2.9828161671E-01 0.0000000000E+00 9.5447790814E-01
-1.4914080836E-01 2.5831945755E-01 9.5447790814E-01
-1.4914080836E-01 -2.5831945755E-01 9.5447790814E-01
#Definition of the atom types
ntypat 2 # There are two types of atoms
znucl 51 52 # Sb, Te
#Definition of the atoms
natom 5 # There are 5 atoms
typat 1 2 2 2 1 # 1 - Sb, 2 - Te
# from previous cell optimization
xred
3.9999873689E-01 3.9999873689E-01 3.9999873689E-01
2.0966603731E-01 2.0966603731E-01 2.0966603731E-01
0.0000000000E+00 0.0000000000E+00 0.0000000000E+00
-2.0966603731E-01 -2.0966603731E-01 -2.0966603731E-01
-3.9999873689E-01 -3.9999873689E-01 -3.9999873689E-01
Then, how should I plot phonon spectrum in anaddb? In particular, anaddb help file said that brav=1 is for all lattices? Then, can I use it with my results for rhombohedral one? And what is the difference between brav=1 and brav=4, e.g. for hexagonal lattice, or brav=1 and brav=2 for FCC?
I am asking because I have plotted phonon spectrum for Si as an exercise. At first I calculate ddb using FCC cell and then plot phonon spectrum using brav=2 and brav=1 - they look similar but for brav=1 - curves look less smooth. But in general: is it correct at all?
Thank you,
dps