<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">
Hello,
<div class=""><br class="">
</div>
<div class="">I am trying to run a lattice optimisation with bulk Titania using the tiorg-0-1 set. I have found the results and minima found depend on which optimiser I use. The following table shows my results using different constraints: free to relax, isotropic
 and fix angles.</div>
<div class=""> </div>
<div style="text-indent: -42.66666793823242px;" class="">             The final result in all cases where the system was allowed to fully relax with no constraints led to a system which was not exactly Tetragonal, which I have found with the settings that are
 reported in the following paper: <span style="text-indent: -32pt;" class="">(1) </span><span style="text-indent: -32pt;" class=""></span><span style="text-indent: -32pt;" class="">Dolgonos, G.; Aradi, B.; Moreira, N. H.; Frauenheim, T. An Improved Self-Consistent-Charge
 Density-Functional Tight-Binding (SCC-DFTB) Set of Parameters for Simulation of Bulk and Molecular Systems Involving Titanium. </span><i style="text-indent: -32pt;" class="">J. Chem. Theory Comput.</i><span style="text-indent: -32pt;" class=""> </span><b style="text-indent: -32pt;" class="">2010</b><span style="text-indent: -32pt;" class="">, </span><i style="text-indent: -32pt;" class="">6</i><span style="text-indent: -32pt;" class=""> (1),
 266–278. </span></div>
<div class=""><br class="">
</div>
<div class="">In each case I used the same starting geometry, (which had previously been generated using DFT therefore I don’t believe it is a poor starting geometry), a k point grid 4 X 4 X 8, SCC tolerance 1E-7, and force tolerance of 1E-4 (unless otherwise
 stated).</div>
<div class=""><br class="">
</div>
<div class=""><!--StartFragment-->
<div style="direction:ltr" class=""><!--StartFragment-->
<div style="direction:ltr" class="">
<table border="1" cellpadding="0" cellspacing="0" valign="top" style="direction:ltr;
 border-collapse:collapse;border-style:solid;border-color:#A3A3A3;border-width:
 1pt" title="" summary="" class="">
<tbody class="">
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">K Point size and optimizer</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">a /Å</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">b/Å</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">c/Å</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">c/a </span>
</div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6868in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Equatorial / Å</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Axial /Å</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Total Energy /eV</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.2in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Band Gap /eV</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 LBFGS Free</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.633</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.634</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997/4.633 = 0.6469
</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.94</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.94</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.94</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.5990</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.8493in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.12</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 LBFGS </span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Angles fixed to 90 degrees</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.607</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.607</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.998</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.998/4.633 = 0.6471
</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.94</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.94</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.5713</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.8493in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.11</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 Fix angles LBFGS
</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Angles fixed to 90 degrees Force tolerance 1E-6</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.632</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.635</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">0.6466</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.99</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.92</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.5990</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.8493in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.12</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 Conjugate Gradient
</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.672</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.672</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997/4.672 = 0.6415
</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.99 <br class="">
1.99</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.99 <br class="">
1.99<br class="">
1.99</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.6037</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.8493in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.13</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 Conjugate Gradient </span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Constraint used: Isotropic</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.643</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.643</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.995</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.995/4.643 = 0.6451
</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.99</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.93</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.93</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.5972</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.8493in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.11</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 CG
</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">Angles fixed to 90 degrees
</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.180</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.180</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.176</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class="">0.999</span></p>
<span style="font-size: 11px;" class=""></span></td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> 3.46</span></p>
<div class=""><span style="font-size: 11px;" class="">3.46<span class="Apple-tab-span" style="white-space:pre">
</span></span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> 1.81</span></p>
<div class=""><span style="font-size: 11px;" class="">1.81</span></div>
<div class=""><span style="font-size: 11px;" class="">1.81</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.4453</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.934in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.928</span></div>
</td>
</tr>
<tr class="">
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:2.1854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4 4 8 gDIIS</span></div>
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> </span></p>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.672</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">4.672</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.0854in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.997/4.672 = 0.6415
</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> 1.99</span></p>
<div class=""><span style="font-size: 11px;" class="">2.00</span></div>
<!--EndFragment--></td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.6673in;padding:4pt 4pt 4pt 4pt" class="">
<p style="margin: 0in;" lang="en-GB" class=""><span style="font-size: 11px;" class=""> 1.93</span></p>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">2.00</span></div>
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">1.92</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:1.5631in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in; font-family: Menlo;" class=""><span style="font-size: 11px;" class="">-425.6037</span></div>
</td>
<td style="border-style:solid;border-color:#A3A3A3;border-width:1pt;
  vertical-align:top;width:.8493in;padding:4pt 4pt 4pt 4pt" class="">
<div style="margin: 0in;" class=""><span style="font-size: 11px;" class="">3.13</span></div>
</td>
</tr>
</tbody>
</table>
</div>
<!--EndFragment--></div>
<!--EndFragment--></div>
<div class=""><br class="">
</div>
<div class="">Although the differences are small, to build slabs requires having the best lattice parameters that I can generate, therefore, I do not want to double any error that might occur depending on which optimiser I use.  </div>
<div class=""><br class="">
</div>
<div class="">The following cases could not converge or showed an error:</div>
<div class="">LBFGS Isotropic - could not optimise by scaling the relative lattice vector </div>
<div class="">gDIIS: could not converge either by fixing angles or using the isotropic setting </div>
<div class=""><br class="">
</div>
<div class="">My main concerns are:</div>
<div class=""><br class="">
</div>
<div class="">
<ul class="MailOutline">
<li class="">Optimisers find different minimas - could there be a bug in the optimizers?</li><li class="">The axial and equatorial bond lengths can vary upto 0.08 /Å, this can lead to problems when building slabs. I have further found that when building 110 slabs, then optimising the geometry, there is a bond length difference is still dependent on
 which optimiser I use</li><li class="">The lowest energy system (Conjugate gradient free to relax) has lattice vectors which are longer than values in comparison, to other results generated and are in worse agreement with experiment and DFT results . I know the differences between all
 the systems are very small, however, these results slightly worry me to what optimiser I should be using when studying further properties. </li></ul>
<div class=""><br class="">
</div>
<div class="">I hope this makes sense.</div>
</div>
<div class=""><br class="">
</div>
<div class="">Many thanks,</div>
<div class=""><br class="">
</div>
<div class="">Laura</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
</body>
</html>