<div dir="auto">Ce is a tricky element with outer electronic configuration 4f1 5d1 6s2 which is open shell. On the other hand Ce(IV) is closed shell. So most quantum chemistry codes struggle to converge for Ce for first few scf cycles. In my experience running an unrestricted calculation (UKS) helps the convergence. However, once first scf cycle is converged things become simpler.</div><div dir="auto"><br></div><div dir="auto">Best,</div><div dir="auto">Debmalya</div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Apr 12, 2023 at 9:57 PM Jessie wang <<a href="mailto:wangchuyan123@gmail.com">wangchuyan123@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><font face="Times New Roman" size="4" style="background-color:white" color="#000000">Dear All,</font><div><font face="Times New Roman" size="4" style="background-color:white" color="#000000"><br></font></div><div><p style="border:0px solid rgb(217,217,227);box-sizing:border-box;margin:0px 0px 1.25em;white-space:pre-wrap"><font face="Times New Roman" size="4" style="background-color:white" color="#000000">I utilized cp2k for DFT+U cell optimization of CeO2, expecting faster processing. However, after testing various parameters for cell optimization, I observed slow SCF convergence, which resulted in a time-consuming cell optimization process of nearly 3 hours.</font></p><p style="border:0px solid rgb(217,217,227);box-sizing:border-box;margin:1.25em 0px;white-space:pre-wrap"><font face="Times New Roman" size="4" style="background-color:white" color="#000000">The reference cell parameters were 5.47 x 5.47 x 5.47. The DA-calculated cell parameters were 5.484, which is acceptable, but it took nearly 3 hours to finished the cell optimization run. However, OT required over 3 hours to complete one ionic step, and never got any information for force.</font></p><p style="border:0px solid rgb(217,217,227);box-sizing:border-box;margin:1.25em 0px;white-space:pre-wrap"><font face="Times New Roman" size="4" style="background-color:white" color="#000000">I have attached my input and output files containing the results for both DA and OT.</font></p><p style="border:0px solid rgb(217,217,227);box-sizing:border-box;margin:1.25em 0px 0px;white-space:pre-wrap"><font face="Times New Roman" size="4" style="background-color:white" color="#000000">I would greatly appreciate any suggestions to address this issue.</font></p></div><div><font face="Times New Roman" size="4" style="background-color:white" color="#000000"><br>Thank you !</font></div><div><font face="Times New Roman" size="4" style="background-color:white" color="#000000"><br></font></div><div><font face="Times New Roman" size="4" style="background-color:white" color="#000000"><br></font></div><div><font face="Times New Roman" size="4" style="background-color:white" color="#000000">Best,</font></div><div><font face="Times New Roman" size="4" style="background-color:white" color="#000000">Jessie</font></div><br>
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