I am nobe to quantum espresso and using supercell for first time.<br>Can any one help me in understanding few things regarding the supecell determination?<br><br>The following is a typical input file I am using (copied from one of the earlier post).<br>
<pre>CONTROL<br>  title = 'Graphene mono layer'<br>  calculation =   "relax"   ,<br>  restart_mode = 'from_scratch' ,<br>  outdir='/home/usuarios/baldini/espresso-4.2.1/tmp/' ,<br>  pseudo_dir = '/home/usuarios/baldini/espresso-4.2.1/pseudo' ,<br>
              etot_conv_thr = 1.0E-4  ,<br>              forc_conv_thr = 1.0D-3 ,<br>              nstep=50,<br>              dt=40,<br>              prefix='1MLG_Ti_H2',<br>/<br>&SYSTEM<br>                      ibrav = 0.,<br>
                      ntyp = 2 ,<br>                      nat = 33 ,<br>                      ecutwfc = 50.0 ,<br>                      ecutrho = 400.0,<br>/<br>&ELECTRONS<br>            electron_maxstep = 300.,<br>            conv_thr  =  1.0d-8  ,<br>
            mixing_mode = 'plain',<br>            mixing_beta = 0.5,<br>            diagonalization   =   'cg' ,<br>            diago_cg_maxiter = 50,<br>/<br>&IONS<br>/<br>CELL_PARAMETERS<br>16.12131954   9.383047808   0.0000000<br>
0.00000000  18.658162370   0.0000000<br>0.0000000    0.0000000    56.6893424<br>ATOMIC_SPECIES<br>C   12.0107   C.pbe-van_ak.UPF<br>Ti  47.8670   Ti.pbe-sp-van_ak.UPF<br>ATOMIC_POSITIONS angstrom<br>C      2.89163        7.40219        1.8862<br>
C      3.59292        8.63832        1.8826<br>C      3.60349        6.16702        1.8884<br>C      5.0186         8.64501        1.8612<br>C      5.0215         6.16598        1.8904<br>C      5.73302        7.40522        1.8718<br>
C      1.47184        7.39616        1.891<br>C      2.89112        9.87066        1.886<br>C      2.89471        4.93264        1.8916<br>C      5.73319        9.8885         1.8612<br>C      5.73643        4.9413         1.8924<br>
C      7.16348        7.41203        1.882<br>C      1.47474        4.9269         1.8924<br>C      0.762281       8.62783        1.8946<br>C      0.763134       6.16172        1.8914<br>C      1.4715         9.86335        1.8934<br>
C      3.60341        11.1095        1.8868<br>C      5.02124        11.1239        1.882<br>C      3.60512        3.70156        1.8932<br>C      5.02645        3.70789        1.891<br>C      7.87807        8.65532        1.8816<br>
C      7.16373        9.89497        1.872<br>C      7.16203        4.94814        1.8954<br>C      7.87619        6.17677        1.8996<br>C      5.73634        12.3522        1.8872<br>C      0.772689       3.69102        1.898<br>
C      0.762793       1.22003        1.8968<br>C      7.87645        11.1337        1.8894<br>C      7.16203        12.3587        1.889<br>C      7.87201        13.5922        1.8942<br>C      2.89479        2.46619        1.8922<br>
C      1.47482        2.45878        1.8952<br>Ti     6.41604        8.65974        3.74<br>K_POINTS {automatic} <br>6.0 6.0 1.0 1.0 1.0 1.0<br><br>Can anyone help me understanding how are these Cell parameters calculated?<br>
Also in some cases celld(m) are used. Can anyone comment on these also?<br>How are the cell parameters and lattice constant or atomic spacing related?<br><br>Any clue would be of great help.<br><br>Thanks in advance.<br><br>
Rgds<br>Deepak<br></pre><br>