As far as i can concern:<br />1)Regularly, if alpha/beta corresponds to spin polarizability, there should be a relationshipf between charge/spin(specifically for each orbital, or combination of them as a whole, the quantity to set total spin is magnetization): <br /><div>charge=-(alpha+beta)/2, magnetization=(alpha-beta)/2, or inversely alpha=magnetization-charge, beta=-charge-magnetization.</div><div><br /></div>2) Multiplicity, is a little bit complex concept. Normally, you can only use 0~2 in cp2k--<br />0: not consider the spin contribution;<br />1: fixed FM state without flipping of spins;<br />2: consider two degree of freedom, up and down;<br /><div>3 and above, only consider deeply magnetic interaction, rather than single electrons, take 2 electrons for example, you might get one singlet plus a set of triplets. * i have not seen any signal that cp2k can handle this issue.</div><div><br /></div><div>3) Perhaps you need add more MOs for proper smearing, usually, empty orbitals does not dirty your calculation result of gap energy.</div><div><br /></div>4) Use $BS instead with seperating atoms of spin up and down in your &coord section, and forget multiplity and magnetization with a # symbol or deleting the line. See page 35/36 in this document- https://www.cp2k.org/_media/events:2015_cecam_tutorial:ling_hybrids.pdf . Nevertheless, during the optimization process, you may not use $BS, but magnetization, and foget #multiplicity.<br /><br />hope these helps.<br /><br />Sigma-Jun LU<br /><br /><div class="gmail_quote"><div dir="auto" class="gmail_attr">在2021年5月5日星期三 UTC+8 15:29:17<ivansc...@gmail.com> 写道:<br/></div><blockquote class="gmail_quote" style="margin: 0 0 0 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Dear all,<div><br></div><div>I come across three different directives, which are all related but confused me, somehow. According to the definition of the manual, we find</div><div><br></div><div><font color="#0000ff">MULTIPLICITY: "<i>Two times the total spin plus one. Specify 3 for a triplet, 4 for a quartet, and so on. Default is 1 (singlet) for an even number and 2 (doublet) for an odd number of electrons.</i>" <br></font></div><div><font color="#0000ff"><br></font></div><div><font color="#0000ff">FIXED_MAGNETIC_MOMENT: "<i>Imposed difference between the numbers of electrons of spin up and spin down: m = n(up) - n(down). A negative value (default) allows for a change of the magnetic moment. -1 specifically keeps an integer number of spin up and spin down electrons.</i>"</font></div><div><font color="#0000ff"><br></font></div><div><font color="#0000ff"> MAGNETIZATION: "<i>The magnetization used in the atomic initial guess. Adds magnetization/2 spin-alpha electrons and removes magnetization/2 spin-beta electrons</i>"</font><br></div><div><br></div><div>I am trying to set magnetic simulations with and without DFT+U corrections for bulk and slabs, both for Ferro-Magnetic (FM) and Anti-Ferro-Magnetic (AFM) ordering. From my experience with other codes, it is first required to set the initial magnetization for the atomic sites. Thus, I would use directive <b>magnetization</b> (BS can be also used but we will not consider it here) when setting the &SUBSYS block. However, I am not sure what this magnetization/2 spin-alpha (-beta) means. </div><div><span style="color:rgb(0,128,0)"><b>Question 1) Can you clarify the meaning of the magnetization/2 is for alpha and beta? What are the units for the magnetization? </b></span><br></div><div><br></div><div>Now let us consider two different cases.</div><div><b>Case A. Solution via diagonalization, smearing and mixing</b><br></div><div>In section &SMEAR we can set FIXED_MAGNETIC_MOMENT to define the difference between electrons up-down (if positive) or allow it to change (if negative). This is very convenient for FM ordering calculations. However, I find it confusing what I should set for MULTIPLICITY in this case. For AFM, one should set FIXED_MAGNETIC_MOMENT=0</div><div>and MULTIPLICITY=1. </div><div><b><span style="color:rgb(0,128,0)">Question 2) For FM systems, one can set the value of FIXED_MAGNETIC_MOMENT and the corresponding value for MULTIPLICITY. However, if I set FIXED_MAGNETIC_MOMENT < 0 (to allow the magnetization to change) what should be the value for MULTIPLICITY? Should it be 0.0? What is the meaning of defining MULTIPLICITY = 0.0 (default)?</span><br></b></div><div><div><font color="#008000"><br></font></div><div><b>Case B. Solution only via OT for systems with band gap</b></div><div>In this case there is no need to introduce &SMEAR. </div><div><font color="#008000"><b>Question 3: CP2K still runs if one sets &OT+&SMEAR+(ADDED_MOL>0, why? Should not the code prevent such simulation?</b></font></div><div>Assuming that we do not include &SMEAR, thus we do not have a way to define the value for FIXED_MAGNETIC_MOMENT. Even tough we can set the initial magnetization, the only way to control the total magnetization/spin is through MULTIPLICITY, but I am not sure if this works correctly for condensed phase systems.<br></div></div><div><div><span style="color:rgb(0,128,0)"><b>Question 4: For AFM states, could I set an initial value of zero from the initial MAGNETIZATION values, and set MULTIPLICITY=1? How do I properly FM states with OT using MAGNETIZATION and MULTIPLICITY?</b></span><br></div><div><br></div></div><div>Thanks a lot for your patience and help to answer my questions</div><div>Ivan</div><div><br></div><div><br></div></blockquote></div>
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