Dear QE users<br>Sir, I am try to find the lattice constant of magnetite (Fe3O4) which is a spinel ferrimagnetic material. The expt lattice constant was 15.87 and I have been trying to find the equilibrium lattice constant (celldm(1)) between 15.80 - 16.00 and all i get is a straight line graph instead of the usual exponential curve graph. I have tried all l could most esp with starting_magnetization but the results are the same. My input is pasted below pls help me to get the appropriate graph.<br>
The kind of the graph I got is attached.<br>Thanks<br><br>&control<br> calculation = 'scf',<br> restart_mode ='from_scratch',<br> prefix = 'Fe3O4',<br> pseudo_dir = '/home/abolore/Programs/Pseudos/',<br>
outdir = './tmp/'<br> /<br> &system<br> ibrav = 2, <br> celldm(1)= $15.80-16.00,<br> nat = 3, <br> ntyp = 3,<br> ecutwfc = 40,<br> ecutrho = 400,<br> starting_magnetization(1) = 0.7,<br>
starting_magnetization(2) = -0.5,<br> starting_magnetization(3) = 0.0,<br> nspin = 2,<br> occupations='smearing',<br> smearing='gaussian',<br> degauss = 0.05,<br> /<br> &electrons<br>
diagonalization = 'david',<br> mixing_mode = 'plain',<br> mixing_beta = 0.7<br> /<br>ATOMIC_SPECIES<br> Fe1 55.845 Fe.pz-nd-rrkjus.UPF<br> Fe2 55.845 Fe.pz-nd-rrkjus.UPF<br> O 16.000 O.pz-rrkjus.UPF<br>
<br>ATOMIC_POSITIONS<br>Fe1 0.125 0.125 0.125 <br>Fe2 0.500 0.500 0.500<br>O 0.2548 0.2548 0.2548<br> <br>K_POINTS (automatic)<br> 8 8 8 1 1 1<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>