Dear Barnali, There is no LO-TO splitting in graphene, or more precisely, it is zero.
Kind regards -- Lorenzo Paulatto Written on a virtual keyboard with real fingers On 30 Nov 2017 3:59 pm, "Barnali Bhattacharya" <[email protected]> wrote: Dear QE USERS, I am trying to reproduce the phonon dispersion with LO-TO splitting of graphene by using quantum espresso code. To get LO-TO splitting, I have added epsil=.true. as well as zeu=.true. in the input file of ph.x. and calculated the phonon modes at q=0 (gamma point). Then I have used dynmat.x. for getting LO-TO splitting. At first, I did not added the propagation direction for q in the input file of dynmat.x . After running dynmat.x, it gives the following line in the output …………………………………………………….. A direction for q was not specified:TO-LO splitting will be absent ……………………………………………. Then I specify the q-point like q(1)=0.01, q(2)=0.0, q(3)=0.00 in the input file of dynmat.x . As a result the above line disappear from the output and the output is something like that ……………………………………………………………………………………………………………………. Reading Dynamical Matrix from file dmat.gra ...Force constants read ...epsilon and Z* read Acoustic Sum Rule: || Z*(ASR) - Z*(orig)|| = 2.089033E-02 Acoustic Sum Rule: ||dyn(ASR) - dyn(orig)||= 1.397683E-04 Polarizability (A^3 units) multiply by 0.417318 for Clausius-Mossotti correction 25.389880 0.000000 0.000000 0.000000 25.389880 0.000000 0.000000 0.000000 1.110081 IR activities are in (D/A)^2/amu units # mode [cm-1] [THz] IR 1 -0.00 -0.0000 0.0000 2 -0.00 -0.0000 0.0000 3 -0.00 -0.0000 0.0000 4 886.97 26.5907 0.0000 5 1701.94 51.0228 0.0000 6 1701.94 51.0228 0.0000 …………………………………………………………………………………………………. So please tell me 1) from which file LO-TO splitting can be found? 2) How can I get the phonon dispersion with LO-TO splitting of graphene? I am waiting for any kind suggestions. For details, I am attaching here the input files and the dispersion curve which I want to reproduce? Thanks in advance. Sincerely Barnali Bhattacharya CSIR SRF, Assam University, Silchar-788011 Assam, INDIA _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
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