[QE-users] CrI3 showed wrong symmetry in optimization

[Pietro Delugas]

Hi your positions are slightly displaced w.r.t the full symmetric ones. 
not that slightly in fact. Using lattice vectors use by pw for ibrav=4   
Cr positions should be something like 
(1/3,2/3,c)  and (2/3,1/3, c)

And  I positions 

(x, 0, c-z), (1-x, 1-x, c-z), (0,x,c-z) 
And 
(1-x,0,c+z), (x,x,c+z), (0,1-x, c+z) 

Hope it helps 
Pietro 

Sent from Mail for Windows 10

From: wang1968000
Sent: Tuesday, September 29, 2020 8:23 AM
To: users
Subject: [QE-users] CrI3 showed wrong symmetry in optimization

Dear QE users,

Thank you for your help. 
I built a monolayer CrI3 structure. However, in the scf calculation, it only find 2 symmetry operation. For monolayer CrI3, it should belong to D3d point group and have 12 symmetry operactions.

Here I attached my input file. Please help me check. Thank you very much for your help.

&control
      calculation = 'vc-relax'
        verbosity = 'high'
     restart_mode = 'from_scratch'
            nstep = 200 
         tstress = .true.
          tprnfor = .true.
    etot_conv_thr = 1.0E-6
    forc_conv_thr = 1.0D-5
       pseudo_dir = '../pp'
           outdir = './tmp/'
           prefix = 'cri3'  
/
&system
            ibrav = 4 
              nat = 8 
             ntyp = 2
	     a = 7.0075147400
             c = 21.3942330000
             nbnd = 80 
          ecutwfc = 180
/
&electrons
         conv_thr = 1.0d-8
      mixing_beta = 0.10 
/
&ions
     ion_dynamics = 'bfgs'
/
&cell
    cell_dynamics = 'bfgs'
   press_conv_thr = 0.01
/
ATOMIC_SPECIES
Cr     51.996    Cr.pz-spn-rrkjus_psl.1.0.0.UPF
I      126.9045  I.pz-n-rrkjus_psl.0.2.UPF
ATOMIC_POSITIONS {crystal}
Cr           0.0000000000       1.0000000000      0.5000000000     
Cr           0.3329150000       0.6670850000      0.5000000000    
I            0.3075660000       0.9749650000      0.4266410000    
I            0.0250350000       0.6924340000      0.5733590000    
I            0.6663520000       0.6927290000      0.4267060000    
I            0.3072710000       0.3336480000      0.5732940000    
I            0.6662030000       0.9747290000      0.5735640000    
I            0.0252710000       0.3337970000      0.4264360000     
K_POINTS {automatic}
8 8 1 0 0 0


Wang
Department of Physics
Tohoku University

 

 

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