<div dir="ltr">I am quite confused about the (lack of) documentation for the XC functionals and non-local vdW. I find examples such as:<div><br></div><div>
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<p class="p1">&XC</p>
<p class="p1">&XC_FUNCTIONAL NO_SHORTCUT</p>
<p class="p1">&LIBXC T</p>
<p class="p1">FUNCTIONAL XC_GGA_X_RPW86</p>
<p class="p1">&END LIBXC </p><p class="p1">&VWN T </p><p class="p1">&END VWN</p>
<p class="p1">&END XC_FUNCTIONAL &VDW_POTENTIAL</p>
<p class="p1">POTENTIAL_TYPE NON_LOCAL &NON_LOCAL</p>
<p class="p1">TYPE LMKLL</p>
<p class="p1">VERBOSE_OUTPUT T KERNEL_FILE_NAME ./vdW_kernel_table.dat CUTOFF 160</p>
<p class="p1">&END NON_LOCAL &END VDW_POTENTIAL</p>
<p class="p1">&END XC</p><p class="p1"><br></p><p class="p1">(from <a href="http://archer.ac.uk/training/course-material/2014/08/CP2K/Slides/NSCCS_2014_Sanliang_Ling.pdf" style="font-family: Arial, Helvetica, sans-serif; font-size: 13px;">http://archer.ac.uk/training/course-material/2014/08/CP2K/Slides/NSCCS_2014_Sanliang_Ling.pdf</a><span style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: 13px;"> )</span></p><p class="p1"><span style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: 13px;"><br></span></p><p class="p1"><span style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: 13px;">and similar even in the regtests.</span></p><p class="p1"><span style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: 13px;">This seems to call both </span>XC_GGA_X_RPW86 and VWN (lda) .</p><p class="p1">What does it mean to call two different xc potentials in cp2k, and why would one do it?</p><p class="p1">Tracing this in the code is not so easy either.</p><p class="p1"><br></p><p class="p1">Ins eom docs it seems to suggest that LDA only should be used for correlation. Is that because GGA is included </p><p class="p1">in the vDW function in cp2k? Also there is the question which pseudopotentials to use.</p><p class="p1"><br></p><p class="p1">It seems to me that XC_GGA_X_RPW86 is correct without the VMN, and this would correapond to what is done for DF2 in</p><p class="p1">quantum espresso it seems.</p><p class="p1"><br></p><p class="p1">I note some related problems with the documentation. I find examples like for LIBXC:</p><p class="p1">
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</p><p class="p1">FUNCTIONAL XC_MGGA_X_M06_L XC_MGGA_C_M06_L</p><p class="p1">but the docs at </p><p class="p1">say</p><ul class="disc" style="color: rgb(0, 0, 0); font-family: Times; font-size: medium;"><li style="margin-left: 0em; padding-left: 0em; text-indent: 0em;"><a href="https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/XC/XC_FUNCTIONAL/LIBXC.html#list_FUNCTIONAL" id="FUNCTIONAL">FUNCTIONAL</a></li><li style="margin-left: 0em; padding-left: 0em; text-indent: 0em;">This keyword cannot be repeated and it expects precisely one word.<br></li></ul><p class="p1">Yet there are "two words" </p><p class="p1">and including VWN afterwards also seems like more than one functional, as I said above.</p><p class="p1"><br></p><p class="p1">Thank you!</p><p class="p1"><br></p><p class="p1">Ronald Cohen</p><p class="p1"><br></p><p class="p1"><span style="color: rgb(34, 34, 34); font-family: Arial, Helvetica, sans-serif; font-size: 13px;"> </span></p><!--?xml version="1.0" encoding="UTF-8"?-->
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