<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">
<div class=""><br class="">
</div>
<div class="">Dear Roberto,</div>
<div class=""><br class="">
</div>
<div class="">in addition to what Lorenzo has already suggested, one more thing to try is to switch on the value of U in small steps. you start from a small value, e.g. 0.01 eV which should go to convergence as smoothly as a plain DFT run does, then you read
potential and wavefunctions and start another run at a bit larger value of U, converge it, restart at a larger value of U and repeat until you reach the value you want to use.</div>
<div class="">In many case where convergence is difficult this helps (even though it may take some steps).</div>
<div class=""><br class="">
</div>
<div class="">Hth.</div>
<div class=""><br class="">
</div>
<div class="">Best,</div>
<div class=""><br class="">
</div>
<div class="">Matteo</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Jul 1, 2018, at 1:45 PM, Lorenzo Paulatto <<a href="mailto:paulatz@gmail.com" class="">paulatz@gmail.com</a>> wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="">On 06/30/2018 04:28 PM, Roberto Gomes de Aguiar Veiga wrote:<br class="">
<blockquote type="cite" class="">However, when I try to perform calculations for the corresponding surfaces, they do not converge. I've been using mixing_mode='local-TF' and descreasing mixing_beta to values as low as 0.05 for the surface calculations, with
no success. Can any of you with experience in this kind of simulation (DFT+U and surfaces) share what you usually do to have converged calculations?<br class="">
</blockquote>
<br class="">
<br class="">
Hello Roberto,<br class="">
DFT+U and surface is a bit tricky, because in principle there is not guarantee that the value of U used for the bulk is transferable to the surface atoms. We all do it, but it is not justified.<br class="">
<br class="">
I also find it very difficult to converge DFT+U for surfaces. One approach I have used is to defined different species for atoms of the uppermost layers and for deeper atoms, to be able to define different starting magnetization. Also, I do not refrain to increase
electrons max steps to 1000 or more, sometimes it just take that long to converge!<br class="">
<br class="">
Finally, a trick which I have used is to use starting_ns_eigenvalue and mixing_fixed_ns to some large value (e.g. 1000) to get a first converged charge density with ns eigenvalues kept fixed, that do a restart="from_scratch" with startingpot="file" (this time
without mixing_fixed_ns, or setting it to a small value).<br class="">
<br class="">
If you notice that the ns eigenvalues printed in output are less symmetric than the initial magnetization, it may be a good idea to split the definition of the +U species until they do, this way you can define different initial ns for them.<br class="">
<br class="">
hth, it is a lot of cooking<br class="">
<br class="">
<br class="">
<br class="">
-- <br class="">
Lorenzo Paulatto - Paris<br class="">
_______________________________________________<br class="">
users mailing list<br class="">
<a href="mailto:users@lists.quantum-espresso.org" class="">users@lists.quantum-espresso.org</a><br class="">
https://lists.quantum-espresso.org/mailman/listinfo/users<br class="">
</div>
</div>
</blockquote>
</div>
<br class="">
<div class=""><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; " class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; "><span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; " class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; " class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; " class="">
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">
<div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; " class="">
<div class=""><br class="Apple-interchange-newline">
************************************************</div>
<div class="">Matteo Cococcioni</div>
<div class="">Theory and Simulation of Materials</div>
<div class="">École Polytechnique Fédérale de Lausanne</div>
</div>
</span><br class="Apple-interchange-newline">
</div>
</span><br class="Apple-interchange-newline">
</div>
</span><br class="Apple-interchange-newline">
</div>
</span><br class="Apple-interchange-newline">
</span><br class="Apple-interchange-newline">
</div>
</span></span></div>
<br class="">
</body>
</html>