<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> </head> <body> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> Hi</div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> <br> </div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> In a first step, I suggest performing test and comparison again using a much tighter SCF convergence threshold than 5.0E-6, e.g. 1.0E-7 or less.</div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> <br> </div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> Best</div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> <br> </div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> Matthias</div> <div dir="ltr" style="font-family: Aptos, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"> <br> </div> <div id="mail-editor-reference-message-container"> <div dir="ltr" class="ms-outlook-mobile-reference-message skipProofing"></div> <div class="ms-outlook-mobile-reference-message skipProofing" style="text-align: left; padding: 3pt 0in 0in; border-width: 1pt medium medium; border-style: solid none none; border-color: rgb(181, 196, 223) currentcolor currentcolor; font-family: Aptos; font-size: 12pt; color: black;"> <b>From: </b>cp2k@googlegroups.com <cp2k@googlegroups.com> on behalf of Richard李 <scarletlotus009@gmail.com><br> <b>Date: </b>Sunday, 30 November 2025 at 14:11<br> <b>To: </b>cp2k <cp2k@googlegroups.com><br> <b>Subject: </b>[CP2K:21990] Questions on small differences in density matrices and Mulliken populations from CP2K single-point calculation<br> <br> </div> <p class="ms-outlook-mobile-reference-message skipProofing">Dear CP2K Developers,</p> <p class="ms-outlook-mobile-reference-message skipProofing">I am writing to ask for your advice regarding some small but systematic discrepancies I observed in density matrices and Mulliken population analysis obtained from a single‐point calculation performed using CP2K.</p> <p class="ms-outlook-mobile-reference-message skipProofing">In my test for CO, I compared the following files generated from the same single-point SCF calculation:</p> <ol start="1"> <li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation"><b>The MOLDEN file</b> (CO_molopt_smearing-mos.molden-1_0.molden)</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation"><b>The Mulliken file</b> (CO_molopt_smearing-mulliken-1.mulliken)</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation"><b>The largest iteration AO log file</b> (e.g., CO_molopt_smearing-ao-1_0_12.Log)</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation"><b>The 1_0 AO log file</b> (CO_molopt_smearing-ao-1_0.Log)</p> </li></ol> <p class="ms-outlook-mobile-reference-message skipProofing">I found that:</p> <ul> <li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">The density matrices read from the last AO log file and from the 1_0 AO file differ by approximately <b>1×10⁻⁷</b>, even though they originate from the same single-point calculation.</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">Constructing Mulliken populations by <b>element-wise multiplication</b> of the density matrix P and the overlap matrix S (i.e., computing PμνSμν for each pair of atomic orbitals) leads to slightly different values compared to the <b>MULLIKEN NET ATOMIC ORBITAL AND OVERLAP POPULATION MATRIX</b> reported in CP2K’s Mulliken output file.</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">Additionally, when processing the MOLDEN file using <b>Multiwfn</b>, the computed Mulliken bond orders are again slightly different from those obtained directly from CP2K.</p> </li></ul> <p class="ms-outlook-mobile-reference-message skipProofing">Before I proceed further, I would like to confirm:</p> <ol start="1"> <li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">Are these ~1e−7 differences expected due to formatting, truncation, numerical precision, or different internal representations used when writing the log files, MOLDEN file, and Mulliken file?</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">Is there a recommended “most reliable” source of the density matrix for reproducing CP2K Mulliken results (Mulliken file vs. AO log file vs. MOLDEN file)?</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">Are the Mulliken matrices produced by CP2K post‐processed in any additional way (e.g., symmetrization, thresholding) that could explain these differences?</p> </li><li> <p class="ms-outlook-mobile-reference-message skipProofing" role="presentation">Are there known limitations or differences in the basis function ordering between MOLDEN export and the AO log files?</p> </li></ol> <p class="ms-outlook-mobile-reference-message skipProofing">For reference, I attach (or can provide) the following files:</p> <div dir="ltr" class="ms-outlook-mobile-reference-message skipProofing">CO_molopt_smearing.inp<br> CO_molopt_smearing.out<br> CO_molopt_smearing-mulliken-1.mulliken<br> CO_molopt_smearing-mos.molden-1_0.molden<br> CO_molopt_smearing-ao-1_0.Log<br> CO_molopt_smearing-ao-1_0_12.Log</div> <p class="ms-outlook-mobile-reference-message skipProofing">Any guidance on how to interpret these discrepancies would be greatly kind of you. Thank you very much for your time and for your continuous development of CP2K.</p> <p class="ms-outlook-mobile-reference-message skipProofing">Best regards</p> <div class="ms-outlook-mobile-reference-message skipProofing">--<br> You received this message because you are subscribed to the Google Groups "cp2k" group.<br> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com" data-outlook-id="6e8d3a27-a3ab-4c5b-baeb-4b28406f1326"> cp2k+unsubscribe@googlegroups.com</a>.<br> To view this discussion visit <a href="https://groups.google.com/d/msgid/cp2k/b263b616-bf70-463b-a9e5-7ad8561fa1e7n%40googlegroups.com?utm_medium=email&utm_source=footer" data-outlook-id="bd9ef870-541d-4e15-8e49-ea5b4809e8e5"> https://groups.google.com/d/msgid/cp2k/b263b616-bf70-463b-a9e5-7ad8561fa1e7n%40googlegroups.com</a>.</div> </div> </body> </html> <p></p> -- <br /> You received this message because you are subscribed to the Google Groups "cp2k" group.<br /> To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>.<br /> To view this discussion visit <a href="https://groups.google.com/d/msgid/cp2k/ZR2P278MB11462FDBC906D9C556471F50F4DBA%40ZR2P278MB1146.CHEP278.PROD.OUTLOOK.COM?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/ZR2P278MB11462FDBC906D9C556471F50F4DBA%40ZR2P278MB1146.CHEP278.PROD.OUTLOOK.COM</a>.<br />