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<div>Hello all, </div>
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<div>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? </div>
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<div>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? </div>
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<div>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. </div>
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<div>Many thanks,</div>
<div>Johannes</div>
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Johannes Moeller </div>
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Department of Physics</div>
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University of Oxford</div>
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Oxford OX1 3PU, UK</div>
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