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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20120921/a765c8d7/attachment.htm
