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    <p>Hello <span style="font-family:Arial,Helvetica,sans-serif">Francisco,</span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">apologies
        for the delay in replying. The spin constants are for the atoms
        and are required for any spin-polarized calculation (there is a
        table in the back of the manual for some parameters, but the
        Slater-Koster parameter files usually come with a list in their
        documentation). The multiplicity is set by choosing the number
        of unpaired spins in the system instead of directly setting
        multiplicity (this is more general, as systems can have
        fractional spin in some cases).</span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">A minimal
        example input for H2+ would look like:</span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">Geometry =
        GenFormat {<br>
        2  C<br>
         H<br>
             1 1 0.0 0.0 0.0<br>
             1 1 0.0 0.0 0.7<br>
        }<br>
        <br>
        Hamiltonian = DFTB {<br>
          SCC = Yes<br>
          MaxAngularMomentum = {<br>
            H = "s"<br>
          }<br>
          Charge = +1<br>
          SpinPolarisation = Colinear {<br>
            UnpairedElectrons = 1 # doublet state<br>
          }<br>
          SpinConstants = { <br>
            H = {<br>
               -6.4E-002<br>
            }<br>
          }<br>
          SlaterKosterFiles = {<br>
            H-H = "H-H.skf"<br>
          }<br>
        }<br>
      </span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">Note that
        unless you use shell resolved spin polarisation (check the
        manual, or examples from the autotest directory), you only give
        the spin constants for the highest occupied atomic orbital for
        each species.</span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif"><br>
      </span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">The
        constrained charge feature you mention was present in an earlier
        version of the code, but was removed. It will probably make a
        return in the next code release (19.2) late this year.</span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">Regards</span></p>
    <p><span style="font-family:Arial,Helvetica,sans-serif">Ben<br>
      </span></p>
    <div class="moz-cite-prefix">On 31/07/2019 02:26, Francisco Adasme
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAGd_1Vaq9ZOS7Hm2j9qzWhGsTvK2+uCQWadM9_JjqWr=DGfU3A@mail.gmail.com">
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          style="font-family:arial,helvetica,sans-serif"><span
            style="font-family:Arial,Helvetica,sans-serif">Dear DFTB+
            members,</span></div>
        <br>
        I'm interested in <span class="gmail_default"
          style="font-family:arial,helvetica,sans-serif">doing some SCC
          calculations on an organic molecule in a radical cation state.
          In pure QM software, I'd set the charge to 1 and multiplicity
          to 2. </span><span
          style="font-family:arial,helvetica,sans-serif">What options
          should I set to model this since there is no multiplicity<span
            class="gmail_default"
            style="font-family:arial,helvetica,sans-serif"> keyword</span>?<span
            class="gmail_default"
            style="font-family:arial,helvetica,sans-serif"> </span></span><span
          style="font-family:arial,helvetica,sans-serif">I found </span><a
href="https://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/2012/000913.html"
          style="font-family:arial,helvetica,sans-serif"
          moz-do-not-send="true">this answer</a><span
          style="font-family:arial,helvetica,sans-serif"> referring to
          the SpinPolarisation option<span class="gmail_default"
            style="font-family:arial,helvetica,sans-serif">, which </span>also
          needs SpinConstants<span class="gmail_default">, but I don't
            know what values to use.</span></span>
        <div><font face="arial, helvetica, sans-serif"><br>
          </font></div>
        <div><font face="arial, helvetica, sans-serif"><span
              class="gmail_default"
              style="font-family:arial,helvetica,sans-serif">Additionally,
              is there a way to constrain the charge to a specified
              molecular fragment?, as I note that other programs support
              this.</span></font></div>
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              <div><br>
                Best regards,<br>
                <div class="gmail_default"
                  style="font-family:arial,helvetica,sans-serif"><span
                    style="font-family:Arial,Helvetica,sans-serif">Francisco.</span></div>
                <div><br>
                </div>
                -- <br>
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                                              <div><font face="arial,
                                                  helvetica, sans-serif">Francisco
                                                  Adasme Carreño</font></div>
                                              <div><font face="arial,
                                                  helvetica, sans-serif">Bioinformatics
                                                  Engineer, PhD</font></div>
                                              <div><font face="arial,
                                                  helvetica, sans-serif">Center
                                                  for Bioinformatics and
                                                  Molecular Simulations,
                                                  CBSM</font></div>
                                              <div><font face="arial,
                                                  helvetica, sans-serif">Universidad
                                                  de Talca</font></div>
                                              <div><font face="arial,
                                                  helvetica, sans-serif">Av.
                                                  Lircay S/N, Talca,
                                                  Chile</font></div>
                                              <div><font face="arial,
                                                  helvetica, sans-serif">T:
                                                  (+56) 71 2 201 798</font></div>
                                              <div><font face="arial,
                                                  helvetica, sans-serif">E:
                                                  <a
                                                    href="mailto:francisco.adasme@gmail.com"
                                                    target="_blank"
                                                    moz-do-not-send="true">francisco.adasme@gmail.com</a>
                                                  or <a
                                                    href="mailto:fadasmec@utalca.cl"
                                                    target="_blank"
                                                    moz-do-not-send="true">fadasmec@utalca.cl</a></font></div>
                                            </div>
                                            <div><font face="arial,
                                                helvetica, sans-serif">URL:
                                                <a
                                                  href="http://about.me/franciscoadasme"
                                                  target="_blank"
                                                  moz-do-not-send="true">http://about.me/franciscoadasme</a>,
                                                <a
                                                  href="https://www.researchgate.net/profile/Francisco_Adasme"
                                                  target="_blank"
                                                  moz-do-not-send="true">https://www.researchgate.net/profile/Francisco_Adasme</a></font></div>
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      <pre class="moz-quote-pre" wrap="">_______________________________________________
DFTB-Plus-User mailing list
<a class="moz-txt-link-abbreviated" href="mailto:DFTB-Plus-User@mailman.zfn.uni-bremen.de">DFTB-Plus-User@mailman.zfn.uni-bremen.de</a>
<a class="moz-txt-link-freetext" href="https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user">https://mailman.zfn.uni-bremen.de/cgi-bin/mailman/listinfo/dftb-plus-user</a></pre>
    </blockquote>
    <pre class="moz-signature" cols="72">-- 
        Dr.  B.  Hourahine,  Senior  lecturer
            SUPA, Department  of  Physics,
             University  of  Strathclyde,
              John  Anderson  Building,
          107 Rottenrow, Glasgow G4 0NG, UK.                  
  +44 141 548 2325, <a class="moz-txt-link-abbreviated" href="mailto:benjamin.hourahine@strath.ac.uk">benjamin.hourahine@strath.ac.uk</a>

The  Department is  a partner  in SUPA,  the Scottish
            Universities Physics Alliance
            
The University  of Strathclyde  is a  charitable body,
       registered in Scotland, number SC015263</pre>
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