On 06/09/2017 11:22, Charlie Ruffman wrote:
Hi all,
I have recently become interested in how the size of the unit cell in
phonon calculations effects the results produced by the calculation
(Raman spectra in particular). It seems that increasing the number of
atoms explicitly simulated should also increase the number of normal
modes calcuated?
It does. these are hovewer modes that would correspond to a q/=0 in the
original primitive cell... as such they should be raman-inactive.
The calculation in the supercell, if properly done (same cutoff,
equivalent k-points, sufficient scf convergence) should be exactly
comparable to the superposition of the results in the primitive cell for
the q-vectors that map into the Gamma point of the supercell.
stefano
Does anyone know if using the primitive cell will produce more or less
accurate results than a larger supercell?
Thanks
--
Charlie Ruffman | BSc
BSc(Hons) Student
Chemistry Department
University of Otago
Tel 64 3 479 7930
PO Box 56, Dunedin 9054
New Zealand
Website _http://neon.otago.ac.nz/research/alg/
<http://neon.otago.ac.nz/research/alg/>_
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