A further addition and good reading why adding k-points to TDDFT might not be that straightforward:
THE JOURNAL OF CHEMICAL PHYSICS 129, 034101 "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?" Artur F. Izmaylov and Gustavo E. Scuseriaa 2011/4/20 O. Baris Malcioglu <baris.malcioglu at gmail.com> > Dear All, > 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? > Best, > Baris > P.S. > (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) > I would recommend you to start with 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). ) > > 2011/4/20 Giuseppe Mattioli <giuseppe.mattioli at mlib.ism.cnr.it> > >> Dear all >> I did not say that TDDFPT does not work with periodic system, but you >> cannot >> have a realistic absorption spectra of a slab (or bulk crystal) if you >> sample >> the Brillouin zone by using Gamma only... TDDFPT works fine with finite >> systems, i.e., which do not show a (strong) k dependence of the psi_n,k >> eigenvalues. >> >> Giuseppe >> >> On Wednesday 20 April 2011 03:00:41 Johari, Priya Sudhir wrote: >> > Thanks Marton, its working. >> > >> > On Tue, Apr 19, 2011 at 5:40 PM, Marci <vormar at gmail.com> wrote: >> > > Dear Priya, >> > > >> > > Though I have never tried, it should work with periodic systems if you >> > > sample the Brillouin zone only with the gamma point. Keep in mind that >> > > the usual adiabatic approximations with (semi)local functionals might >> > > not work very well for calculating the absorption of periodic systems. >> > > >> > > Marton >> > > >> > > -- >> > > Marton Voros >> > > PhD student >> > > Department of Atomic Physics >> > > Budapest University of Technology and Economics >> > > Budafoki ?t 8., H-1111, Budapest, Hungary >> > > www.fat.bme.hu/MartonVoros >> > > >> > > On Tue, Apr 19, 2011 at 11:02 PM, Johari, Priya Sudhir >> > > >> > > <priya_johari at brown.edu> wrote: >> > > > Thanks Duy, but the link does not give sufficient information. >> However, >> > > > I found a discussion on forum's archive itself where Giuseppe >> Mattioli >> > > > has mentioned that TDDPFT does not work for periodic systems :-( >> > > > >> > > > Dr Priya Johari. >> > > > Brown University, >> > > > Providence, RI - 02906. USA >> > > > >> > > > On Tue, Apr 19, 2011 at 3:59 PM, Duy Le <ttduyle at gmail.com> wrote: >> > > >> If you do a little homework (such as googling keyword TD-DFPT), >> you'll >> > > >> find this link >> > > >> http://qe-forge.org/projects/tddfpt/ >> > > >> I have not read it carefully but I guess it contains some useful >> > > >> information. >> > > >> -------------------------------------------------- >> > > >> Duy Le >> > > >> PhD Student >> > > >> Department of Physics >> > > >> University of Central Florida. >> > > >> >> > > >> "Men don't need hand to do things" >> > > >> >> > > >> >> > > >> >> > > >> On Tue, Apr 19, 2011 at 3:26 PM, Johari, Priya Sudhir >> > > >> >> > > >> <priya_johari at brown.edu> wrote: >> > > >> > TD-DFPT >> > > >> >> > > >> _______________________________________________ >> > > >> Pw_forum mailing list >> > > >> Pw_forum at pwscf.org >> > > >> http://www.democritos.it/mailman/listinfo/pw_forum >> > > > >> > > > _______________________________________________ >> > > > Pw_forum mailing list >> > > > Pw_forum at pwscf.org >> > > > http://www.democritos.it/mailman/listinfo/pw_forum >> > > >> > > _______________________________________________ >> > > Pw_forum mailing list >> > > Pw_forum at pwscf.org >> > > http://www.democritos.it/mailman/listinfo/pw_forum >> >> >> >> -- >> ******************************************************** >> - Article premier - Les hommes naissent et demeurent >> libres et ?gaux en droits. Les distinctions sociales >> ne peuvent ?tre fond?es que sur l'utilit? commune >> - Article 2 - Le but de toute association politique >> est la conservation des droits naturels et >> imprescriptibles de l'homme. Ces droits sont la libert?, >> la propri?t?, la s?ret? et la r?sistance ? l'oppression. >> ******************************************************** >> >> Giuseppe Mattioli >> CNR - ISTITUTO DI STRUTTURA DELLA MATERIA >> v. Salaria Km 29,300 - C.P. 10 >> I 00015 - Monterotondo Stazione (RM) >> Tel + 39 06 90672836 - Fax +39 06 90672316 >> E-mail: <giuseppe.mattioli at ism.cnr.it> >> _______________________________________________ >> Pw_forum mailing list >> Pw_forum at pwscf.org >> http://www.democritos.it/mailman/listinfo/pw_forum >> > > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110420/3eec04df/attachment.htm
