[Pw_forum] S matrix not positive definite

[2lgy]

Dear all,
I want to calculate the Raman tensor. I First do a scf calculation (pw.x), followed by PHonon calculation (ph.x), and I got the following message:


 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine cdiaghg (5):
     S matrix not positive definite
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


Input file for pw.x is
&CONTROL
 title = scf,
 prefix = 'graphene'
 calculation = 'scf' ,
 restart_mode = 'from_scratch' ,
 wf_collect = .false. ,
 outdir = './' ,
 pseudo_dir = '~/ppqe' ,
 etot_conv_thr = 1.0d-5 ,
 forc_conv_thr = 1.0d-4 ,
 tstress = .true. ,
 tprnfor = .true. ,
 nstep = 100 ,
/
&SYSTEM
 ibrav = 4,
 celldm(1) = 4.5961617417745675,
 celldm(3) = 10,
 nat = 2,
 ntyp = 1,
 ecutwfc = 80,
 nosym = .false. ,
/
&ELECTRONS
 electron_maxstep = 100,
 conv_thr = 1.D-12,
 mixing_beta = 0.3
/
ATOMIC_SPECIES
 C   14.0067   C.pz-hgh.UPF
ATOMIC_POSITIONS crystal
C   0.0   0.0   0.0
C   1/3  -1/3   0.0
K_POINTS automatic
  16 16 1 0 0 0


The input file for ph.x is
phonon
&inputph
  tr2_ph=1.0d-14,
  prefix='graphene',
  epsil=.true.,
  trans=.true.,
  lraman=.true.,
  amass(1)=12.0,
  outdir='./',
  fildyn='graphene_ir.dynG',
  fildrho='graphene_ir.drho',
/
0.0 0.0 0.0


I have tried to calculate the Raman tensor of ZnS with the same procedure, and every thing goes well. But when I use similar input files for graphene, it failed.


Graphene is a 2-dimensional system, while ZnS is a 3-dimensional crystal. I don't know if this difference is responsible for this failure, since, for 2D system, I have to insert a large vacuum, which is a potential source of problem.


Thanks in advance!








--


Sincerely Yours

Jason Lee(李杰森)

----------------------------------------------------
Jason Lee
Ph.D in Physics; President of Sanda Association; Doctoral Student Union
School of Physics and Engineering
Sun Yat-sen University, 135#Xingang Xi Rd.
Guangzhou, 510275, China
Tel：020-84111107(office) Cell: 13560161944(661944)








 
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