<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><br><div><div>On May 9, 2011, at 5:36 AM, swapnil chandratre wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">Hi, I have prepared an input file for a porous graphene nanoribbon, can anyone please comment if there are any errors with the file.</blockquote><div><br></div>it is always a good idea to open the input file using XCrysDen (or any other visualization software with a working Quantum-ESPRESSO interface),</div><div>because this often helps in pointing out "structural" (cell paramenters and/or atomic positions) issues (see below).</div><div><br><blockquote type="cite"><div><div>ecutwfc=80.0</div><div>ecutrho = 600.0</div></div></blockquote>.....<br><blockquote type="cite"><div><div>C 12.0000 C.pz-rrkjus.UPF</div><div>H 1.00000 H.pz-rrkjus.UPF</div><div><font class="Apple-style-span" color="#000000"><font class="Apple-style-span" color="#144FAE"><br></font></font></div></div></blockquote><div>because your pseudos are ultrasoft a 80 Ry cutoff is likely very huge,</div><div>you can reach convergence with much lower values, I think.</div><div><br></div><div><br></div><div>Concerning the structural part, there is a problem for sure.</div><div><blockquote type="cite"><div><div>CELL_PARAMETERS</div><div>19.200000 0.000000 0.000000 </div><div>0.0000000 21.90350 0.000000</div><div>0.0000000 0.000000 10.00000</div></div></blockquote></div><div>you chose an orthorombic unit cell with axis lengths of</div><div>about 10, 11.4 and 5,0 Angstrom, respectively. </div><div><br></div><div>But if you look at the atomic positions,</div><div>you can easily see that:</div><div><div><blockquote type="cite"><div><div> C 0.710430 9.644997 5.000000</div></div></blockquote></div><div><blockquote type="cite"><div><div> H 20.44254 5.000000 5.000000</div></div></blockquote><div><br></div>the x coordinates of these two atoms differ by 20.4 - 0.7 = 19.7 A which is less than your unit cell size along the x axis.</div><div>The mistake probably originates from the fact that if you DO NOT specify celldm(1), the units of coordinates within the CELL_PARAMETERS card</div><div>is a.u., namely, Bohr. I guess that you want to specify those units in Angstrom, indeed, the structure looks much better (with a hole that is what you mean with "porous") if you set celldm(1)=1.889727</div><div>(inverse of Bohr). Anyway, orthorombic cells are much easier specified by setting ibrav=8 and then a, b, c as axis lengths in Angstrom (see Doc/INPUT_PW.txt).</div><div><br></div><div>Even after correctly specifying axis length units there is still a problem with the above atoms, because the 19.7 A difference of x coordinates is still larger than the 19.2 Angstrom a-axis. So, either</div><div>the atomic positions are wrong, or the cell size was incorrectly computed.</div><div><br></div><div>Giovanni</div><div><br></div><div><br></div></div></div><div>
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