<div dir="ltr"><div dir="ltr"><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal">Dear DFTB+ users,<br>I am trying to optimize the molecules in the unit cell of C10-DNBDT (see gen and cif files attached) without changing the lattice constants. I am using DFTB+ 18.2, the Conjugate Gradient method and Supercell Folding k-points. <br>Unfortunately, I did not manage to reach convergence, as the Maximal force component oscillates between 10^-3 and 10^-2, even after several (more than 1000) Geometry steps. </div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal"><br>Since in the past I have managed to optimize several organic molecules (rubrene, pentacene, DNTT, etc,) I honestly do not understand what I am doing wrong.<br>Following some threads I have found online, I have also tried to change the number of k-points (2, 1 and 6 instead of 4) but I still got the same problem: the Maximal force component oscillates between 10^-3 and 10^-2.</div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal"><br></div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal">Could you please give me any suggestions on what I should do in order to reach geometry convergence?</div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal"><br></div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal"><br>Thank you in advance.</div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal"><br></div><div style="text-align:left;color:rgb(34,34,34);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:Arial,Helvetica,sans-serif;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal">Best regards,<br>Alessandro</div><br clear="all"><br>-- <br><div class="gmail_signature" dir="ltr"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div style="margin:0px;padding:0px;text-align:left;color:rgb(51,51,51);text-transform:none;text-indent:0px;letter-spacing:normal;font-family:monospace;font-size:13.33px;font-style:normal;font-variant:normal;font-weight:400;text-decoration:none;word-spacing:0px;white-space:normal;background-color:transparent"><span style="color:rgb(128,128,128)">Alessandro Landi, Assegnista di Ricerca</span><br><span style="color:rgb(128,128,128)"> Dipartimento di Chimica e Biologia "Adolfo Zambelli"</span><br><span style="color:rgb(128,128,128)"> Università degli Studi di Salerno </span><br><span style="color:rgb(128,128,128)"> Via Giovanni Paolo II, 132 - 84084 - Fisciano (SA)</span><br><span style="color:rgb(128,128,128)">Phone number 089969390</span></div></div></div></div></div></div></div></div></div>