A further addition and good reading why adding k-points to TDDFT might not be that straightforward: <div><br><div>THE JOURNAL OF CHEMICAL PHYSICS 129, 034101 </div><div>"Why are time-dependent density functional theory excitations in solids equal to band structure energy gaps for semilocal functionals, and how does nonlocal Hartree–Fock-type exchange introduce excitonic effects?"</div>
<div>Artur F. Izmaylov and Gustavo E. Scuseriaa<br>
<br><div class="gmail_quote">2011/4/20 O. Baris Malcioglu <span dir="ltr"><<a href="mailto:baris.malcioglu@gmail.com" target="_blank">baris.malcioglu@gmail.com</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Dear All, <div>The current implementation of TDDFPT in Q-E is intended for "standalone" systems (i.e. non bulk, solvated or encapsulated in dielectric systems are ok). You will see confinement effects in lower dimensional systems (including 1D and 2D systems) in the non-extended dimensionality(-ies) save excitations with strong Mott-Wannier like character (CT excitations in theoretical chemistry) since the oscillator strength for them in the current implementation goes to zero due to ALDA (working on that). For the extended dimensions you'll see no accountable difference from run-of-the-mill DFT-RPA save if there is an extraordinarily strongly bound exciton at gamma point (i.e. strongly ionic materials) (please see how TDDFT is formulated through response -charge-, and how K points may come into play). For "ordinary" bulk materials, frequency dependence and long range tail of the kernel is generally mandatory for a bound exciton, which is quite "tricky" to add I would say (beware of EXX and TD-HF, they tend to have quite wrong exciton binding energies, personally I think this is due to lack of inclusion of a proper generalised dielectric function in their formulation). If you want to study "ordinary bulk materials" I would recommend you BSP or TD-CFT whenever GW can not save the day. Did you try SAX?</div>
<div>Best,</div><div>Baris</div><div>P.S. </div><div>(There are many books on the topic, especially regarding what to expect and what not to expect from TDDFT, my personal opinion is that TDDFT thrives in the realm between theoretical chemistry and bulk materials, i.e. large molecules, nanocrystals, etc. Then again, this is my personal opinion) </div>
<div>I would recommend you to start with <span style="font-family:sans-serif;font-size:13px;line-height:19px">M.A.L. Marques, C.A. Ullrich, F. Nogueira, A. Rubio, K. Burke, and E.K.U. Gross (eds.), Time-Dependent Density Functional Theory (Springer-Verlag, 2006). )</span> </div>
<div><div></div><div>
<div><br><div class="gmail_quote">2011/4/20 Giuseppe Mattioli <span dir="ltr"><<a href="mailto:giuseppe.mattioli@mlib.ism.cnr.it" target="_blank">giuseppe.mattioli@mlib.ism.cnr.it</a>></span><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear all<br>
I did not say that TDDFPT does not work with periodic system, but you cannot<br>
have a realistic absorption spectra of a slab (or bulk crystal) if you sample<br>
the Brillouin zone by using Gamma only... TDDFPT works fine with finite<br>
systems, i.e., which do not show a (strong) k dependence of the psi_n,k<br>
eigenvalues.<br>
<br>
Giuseppe<br>
<div><div></div><div><br>
On Wednesday 20 April 2011 03:00:41 Johari, Priya Sudhir wrote:<br>
> Thanks Marton, its working.<br>
><br>
> On Tue, Apr 19, 2011 at 5:40 PM, Marci <<a href="mailto:vormar@gmail.com" target="_blank">vormar@gmail.com</a>> wrote:<br>
> > Dear Priya,<br>
> ><br>
> > Though I have never tried, it should work with periodic systems if you<br>
> > sample the Brillouin zone only with the gamma point. Keep in mind that<br>
> > the usual adiabatic approximations with (semi)local functionals might<br>
> > not work very well for calculating the absorption of periodic systems.<br>
> ><br>
> > Marton<br>
> ><br>
> > --<br>
> > Marton Voros<br>
> > PhD student<br>
> > Department of Atomic Physics<br>
> > Budapest University of Technology and Economics<br>
> > Budafoki út 8., H-1111, Budapest, Hungary<br>
> > <a href="http://www.fat.bme.hu/MartonVoros" target="_blank">www.fat.bme.hu/MartonVoros</a><br>
> ><br>
> > On Tue, Apr 19, 2011 at 11:02 PM, Johari, Priya Sudhir<br>
> ><br>
> > <<a href="mailto:priya_johari@brown.edu" target="_blank">priya_johari@brown.edu</a>> wrote:<br>
> > > Thanks Duy, but the link does not give sufficient information. However,<br>
> > > I found a discussion on forum's archive itself where Giuseppe Mattioli<br>
> > > has mentioned that TDDPFT does not work for periodic systems :-(<br>
> > ><br>
> > > Dr Priya Johari.<br>
> > > Brown University,<br>
> > > Providence, RI - 02906. USA<br>
> > ><br>
> > > On Tue, Apr 19, 2011 at 3:59 PM, Duy Le <<a href="mailto:ttduyle@gmail.com" target="_blank">ttduyle@gmail.com</a>> wrote:<br>
> > >> If you do a little homework (such as googling keyword TD-DFPT), you'll<br>
> > >> find this link<br>
> > >> <a href="http://qe-forge.org/projects/tddfpt/" target="_blank">http://qe-forge.org/projects/tddfpt/</a><br>
> > >> I have not read it carefully but I guess it contains some useful<br>
> > >> information.<br>
> > >> --------------------------------------------------<br>
> > >> Duy Le<br>
> > >> PhD Student<br>
> > >> Department of Physics<br>
> > >> University of Central Florida.<br>
> > >><br>
> > >> "Men don't need hand to do things"<br>
> > >><br>
> > >><br>
> > >><br>
> > >> On Tue, Apr 19, 2011 at 3:26 PM, Johari, Priya Sudhir<br>
> > >><br>
> > >> <<a href="mailto:priya_johari@brown.edu" target="_blank">priya_johari@brown.edu</a>> wrote:<br>
> > >> > TD-DFPT<br>
> > >><br>
> > >> _______________________________________________<br>
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