ABINIT Discussion Forums

Dear all,
I just use abinit to calculate graphene's electron-phonon interaction. The detail data of GS+RF is:

ndtset 26

# DATASET 1:make GS_SCF wavefunctions and density

kptopt1 1

prtwf1 1
prtden1 1
tolvrs1 1.0d-20
getwfk1 0
rfphon1 0
nqpt1 0

# DATASET 2-26:make a RF calculation and get gkk and ddb
qpt2 0.00000000E+00 0.00000000E+00 0.00000000E+00
qpt3 1.11111111E-01 0.00000000E+00 0.00000000E+00
qpt4 2.22222222E-01 0.00000000E+00 0.00000000E+00
qpt5 3.33333333E-01 0.00000000E+00 0.00000000E+00
qpt6 4.44444444E-01 0.00000000E+00 0.00000000E+00
qpt7 0.00000000E+00 1.11111111E-01 0.00000000E+00
qpt8 1.11111111E-01 1.11111111E-01 0.00000000E+00
qpt9 2.22222222E-01 1.11111111E-01 0.00000000E+00
qpt10 3.33333333E-01 1.11111111E-01 0.00000000E+00
qpt11 4.44444444E-01 1.11111111E-01 0.00000000E+00
qpt12 -4.44444444E-01 1.11111111E-01 0.00000000E+00
qpt13 -3.33333333E-01 1.11111111E-01 0.00000000E+00
qpt14 -2.22222222E-01 1.11111111E-01 0.00000000E+00
qpt15 0.00000000E+00 2.22222222E-01 0.00000000E+00
qpt16 1.11111111E-01 2.22222222E-01 0.00000000E+00
qpt17 2.22222222E-01 2.22222222E-01 0.00000000E+00
qpt18 3.33333333E-01 2.22222222E-01 0.00000000E+00
qpt19 4.44444444E-01 2.22222222E-01 0.00000000E+00
qpt20 -4.44444444E-01 2.22222222E-01 0.00000000E+00
qpt21 0.00000000E+00 3.33333333E-01 0.00000000E+00
qpt22 1.11111111E-01 3.33333333E-01 0.00000000E+00
qpt23 2.22222222E-01 3.33333333E-01 0.00000000E+00
qpt24 3.33333333E-01 3.33333333E-01 0.00000000E+00
qpt25 0.00000000E+00 4.44444444E-01 0.00000000E+00
qpt26 1.11111111E-01 4.44444444E-01 0.00000000E+00

#Common input variables

nqpt 1
kptopt 3
rfphon 1
rfatpol 1 2
rfdir 1 1 1
getwfk 1
prepgkk 1
prtgkk 1
prtwf 1
tolvrs 1.0d-16
iscf 7
ngkpt 72 72 1
nshiftk 1
shiftk 0.0 0.0 0.5

#Definition of the unit cell
acell 4.6508814631E+00 4.6508119417E+00 1.4008039086E+01

rprim 1.0000000000E+00 0.0000000000E+00 0.0000000000E+00
-5.0000747411E-01 8.6602108856E-01 0.0000000000E+00
0.0000000000E+00 0.0000000000E+00 1.0000000000E+00

#Definition of the atom types
ntypat 1
znucl 6

#Definition of the atoms
natom 2 # There are two atoms
typat 1 1

xred 6.6666765924E-01 3.3333531848E-01 2.6727647101E-51
3.3333234076E-01 6.6666468152E-01 -2.6727647101E-51

#Gives the number of band, explicitely (do not take the default)
nband 16
occopt 3
#Exchange-correlation functional

ixc 1 # LDA Teter Pade parametrization

#Definition of the planewave basis set

ecut 40.0 # Maximal kinetic energy cut-off, in Hartree

#Definition of the SCF procedure (dummy)
nstep 500
diemac 12.0

The anaddb.in is :
elphflag 1
nqpath 4
qpath
0.0 0.0 0.0 # gamma
0.5 0.0 0.0 # M
1/3 1/3 0.0 # K
0.0 0.0 0.0 # gamma

ngqpt 9 9 1

asr 2
dipdip 1

# bravais lattice necessary
brav 1

# qpt grid
nqshft 1
q1shft 0.0 0.0 0.0
#
ifcflag 1
ifcana 1
# ifc for all atoms?
natifc 2
atifc 1 2
ifcout 3
# print dielectric matrix with freq dependence
dieflag 0

# print out eigenvectors and symmetrize dyn matrix
eivec 1

#Wavevector list number 1 (Reduced coordinates and normalization factor)
#nph1l 1
#qph1l
# 0.00000000E+00 0.00000000E+00 0.00000000E+00 1

# This line added when defaults were changed (v5.3) to keep the previous, old behaviour
symdynmat 0
#enunit 1
ep_prt_yambo 1

prtdos 1
ng2qpt 48 48 1

elphsmear 0.01

I just use the _ep_BST file to paint the phonon structure of graphene. The picture is:

However, the curve is good except LO phonon during M-K. And the calculated frequency of LO and TO modes at Gamma (1519 cm^-1) is smaller than the previous value of 1595 cm^-1.
I'dont know why . I just use k-mesh of 72 72 1 and q-mesh of 9 9 1.Can you help me ?
Best wishs!

xijinyang

Hello,

what is wrong with the mode between M and K, and what do you mean by "previous" value at Gamma (you don't state if it's the LO or TO mode)?

The BS looks ok, so far. There are published versions in the literature, so you can compare. There are delicate effects due to Kohn anomalies and many body electron effects (see papers in PRB PRL by Francesco Mauri, Ludger Wirtz, and/or Claudio Attaccalite). These are beyond the calculation you are doing here...

Matthieu