[QE-users] Crystal Structure changes after vc-relax

[1806028 - Md. Nure- Alam-Dipu]

Hi altruists,
I am on quantum espresso v6.6. I am trying to do vc-relax of a doped structure of MoTe2 supercell (2x2x1) which has 12 atoms in the supercell and hexagonal symmetry (ibrav = 4). I've replaced 2 Mo atoms with Co atoms and done vc-relax calculation. But after the vc-relax the ibrav has been changed to 9 which says orthorhombic base-c#1 in burai. But I want to keep ibrav = 4. How can I solve this problem?

input:

&CONTROL
    calculation   = "vc-relax"
    etot_conv_thr = 7.3e-07
    forc_conv_thr = 3.9e-04
    max_seconds   =  1.72800e+06
    nstep = 400
    prefix = "MoTe2-Co50%"
    outdir        = "./out/"
    pseudo_dir    = "/home/user/ZTHESIS/pp/"
/

&SYSTEM
    a                         =  7.10408e+00
    c                         =  1.90697e+01
    degauss                   =  0.01
    ecutrho                   =  600
    ecutwfc                   =  60
    ibrav                     = 4
    nat                       = 12
    nspin                     = 2
    ntyp                      = 3
    occupations               = "smearing"
    smearing                  = "gaussian"
    starting_magnetization(1) =  0.01
    starting_magnetization(2) =  2.00000e-01
    starting_magnetization(3) =  2.00000e-01
/

&ELECTRONS
    conv_thr         =  1.00000e-08
    electron_maxstep =  800
    mixing_beta      =  4.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"
/

&IONS
    ion_dynamics = "bfgs"
/

&CELL
    cell_dofree    = "2Dxy"
    cell_dynamics  = "bfgs"
    press_conv_thr =  0.01
/

K_POINTS {automatic}
 5  5  1  0 0 0

ATOMIC_SPECIES
Te    127.60000  Te.pbe-n-kjpaw_psl.1.0.0.UPF
Mo     95.94000  Mo.pbe-spn-kjpaw_psl.1.0.0.UPF
Co     58.93320  Co.pbe-spn-kjpaw_psl.0.3.1.UPF

ATOMIC_POSITIONS {angstrom}
Te      1.776017   1.025388  11.489668
Te      5.328065   1.025388  11.489668
Te     -0.000004   4.101546  11.489668
Te      3.552037   4.101546  11.489668
Mo     -0.000000   2.050776   9.677219
Co      3.552041   2.050776   9.677219
Co     -1.776024   5.126940   9.677219
Mo      1.776017   5.126940   9.677219
Te      1.776017   1.025388   7.864769
Te      5.328065   1.025388   7.864769
Te     -0.000004   4.101546   7.864769
Te      3.552037   4.101546   7.864769

outfut file:

CELL_PARAMETERS (alat= 13.42476557)
   0.999096066  -0.010292564   0.000000000
  -0.508461655   0.860096292   0.000000000
   0.000000000   0.000000000   2.684330694

ATOMIC_POSITIONS (angstrom)
Te            1.7732003335        0.9886410778       11.1741358650
Te            5.2880507458        0.9716634228       11.6046381778
Te           -0.0668794451        4.0633298148       11.6046091343
Te            3.5159185225        4.0071186548       11.1741358650
Mo           -0.2804970380        2.1742960198        9.6773576520
Co            3.8175752171        1.8206429294        9.6769038828
Co           -1.5373523249        4.9123159459        9.6768874481
Mo            1.4622629679        5.1928572784        9.6773576520
Te            1.7731234820        0.9886995072        8.1803422550
Te            5.2883192195        0.9715084194        7.7499499103
Te           -0.0665942024        4.0631651299        7.7499639025
Te            3.5158294953        4.0071559955        8.1803422550
End final coordinates



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