www.democritos.it/pipermail/pw_forum/2008-September/010123.html</a></div>
<div><a href=3D"http://www.democritos.it/pipermail/pw_forum/2010-February.t= xt" target=3D"_blank">http://www.democritos.it/pipermail/pw_forum/2010-Febr= uary.txt</a></div><div><br></div><div>I understand that the third derivativ= es were never implemented and</div> <div>that only the LDA part was calculated, for the Perdew Zunger</div><div= >parameterization. Is this third derivative the third derivative that</div>= <div>is mentioned in the routine PH/raman_mat.f90 (i.e, the third</div> <div>derivative of the energy with respect to the atomic displacements and<= /div><div>with respect to two electric fields, as described in Lazzeri and<= /div><div>Mauri, PRL 90,036401)?</div><div><br></div><div>I am interested i= n getting a feel for what would be needed to</div> <div>implement the third derivatives with GGA into the code, as well as</di= v><div>what sort of errors one might expect when using the third-order term= </div><div>as currently coded with LDA pseudopotentials (comments in the fo= rums</div> <div>have hinted that the errors are likely small). =A0The shift in the Ram= an</div><div>spectra for cd-Si is pretty minor when using a GGA pseudo comp= ared to</div><div>that of an LDA calculation, but I wanted to be able to qu= antify the</div> <div>error better for other systems where comparing the GGA raman spectra</= div><div>to one calculated within LDA was not possible (e.g., when the syst= em</div><div>doesn't exhibit a gap in LDA).</div><div><br></div><div> Thanks for the help!</div><div><br></div><div>Best,</div><div>Brad</div><di= v>UC Berkeley</div></div></div><div><div></div><div class=3D"h5"><div><div>= <br></div><br><div class=3D"gmail_quote">On Tue, Nov 9, 2010 at 5:59 PM, Br= ad Malone <span dir=3D"ltr"><<a href=3D"mailto:brad.malone at gmail.com" ta= rget=3D"_blank">brad.malone at gmail.com</a>></span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex">It appears that my last email was severely t= runcated on the mailing list (even though it looks fine in my outbox). Belo= w is what is should have been:<div> -----------------------</div><div><div><div></div><div><span style=3D"font-= family:arial, sans-serif;font-size:13px;border-collapse:collapse;color:rgb(= 51, 51, 51)">Hi, I am seeking more information on the error<br> <br>> from phq_setup : error # 1<br>> third order derivatives not imp= lemented with GGA<br><br>From the forums:<br><br><a href=3D"http://www.demo= critos.it/pipermail/pw_forum/2008-September/010123.html" style=3D"color:rgb= (61, 84, 89)" target=3D"_blank">http://www.democritos.it/pipermail/pw_forum= /2008-September/010123.html</a><br> <a href=3D"http://www.democritos.it/pipermail/pw_forum/2010-February.txt"; s= tyle=3D"color:rgb(61, 84, 89)" target=3D"_blank">http://www.democritos.it/p= ipermail/pw_forum/2010-February.txt</a><br><br>I understand that the third = derivatives were never implemented and<br> that only the LDA part was calculated, for the Perdew Zunger<br>parameteriz= ation. Is this third derivative the third derivative that<br>is mentioned i= n the routine PH/raman_mat.f90 (i.e, the third<br>derivative of the energy = with respect to the atomic displacements and<br> with respect to two electric fields, as described in Lazzeri and<br>Mauri, = PRL 90,036401)?<br><br>I am interested in getting a feel for what would be = needed to<br>implement the third derivatives with GGA into the code, as wel= l as<br> what sort of errors one might expect when using the third-order term<br>as = currently coded with LDA pseudopotentials (comments in the forums<br>have h= inted that the errors are likely small). =A0The shift in the Raman<br>spect= ra for cd-Si is pretty minor when using a GGA pseudo compared to<br> that of an LDA calculation, but I wanted to be able to quantify the<br>erro= r better for other systems where comparing the GGA raman spectra<br>to one = calculated within LDA was not possible (e.g., when the system<br>doesn'= t exhibit a gap in LDA).<br> <br>Thanks for the help!<br><br>Best,<br>Brad<br>UC Berkeley</span><br><br>= </div></div><div><div></div><div><div class=3D"gmail_quote">On Tue, Nov 9, = 2010 at 5:00 PM, Brad Malone <span dir=3D"ltr"><<a href=3D"mailto:brad.m= alone at gmail.com" target=3D"_blank">brad.malone at gmail.com</a>></span> wro= te:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex">Hi, I am seeking more information on the err= or<br> <br> > from phq_setup : error # 1<br> > third order derivatives not implemented with GGA<br> <br>
