Yes, you are right. The numbers with units /cm are wavenumbers (nu-bar). Frequency, nu (/s) = c (cm/s) * nu-bar (/cm) Lamda (cm) = 1/nu-bar (/cm) Energy = hbar (energy-s) * nu (/s)
Saurabh Bajaj California Institute of Technology On Fri, Sep 21, 2012 at 9:25 AM, Johannes Moeller < j.moeller1 at physics.ox.ac.uk> wrote: > Hello all, > > A quick question about the definition of the phonon frequency omega. Is > the omega output by Espresso an angular or a linear frequency (omega/2pi)? > I.e. is this converted into an energy by multiplying by hbar or h? > > Comparing simple vibrational modes of molecules (eg. of CO2) in cm^-1 to > experimental values gives good agreement with experimental data, which are > usually referred to as a liner frequency nu or 1/lambda rather than an > angular frequency omega. This suggests that the value that Espresso outputs > is nu and not omega(2pi*nu) as the name implies? > > The values output by Espresso in THz and cm^-1 seem to be related simply > by a factor of c (no factors of 2pi). I'm using QE 5.01 but I don't think > this is version specific. > > Many thanks, > Johannes > > ------------------------------- > Johannes Moeller > Department of Physics > University of Oxford > Parks Road > Oxford OX1 3PU, UK > > > _______________________________________________ > 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/20120921/5b7155d3/attachment-0001.htm
