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[Matthieu Verstraete <mjv500@york.ac.uk>]

> As pointed out in the help file, "heat capacity C(J/(mol-c.K)) (A mol-c 
> is the abbreviation of a mole-cell, that is, the number of Avogadro 
> times the atoms in a unit cell) calinterested in the phonon calculation 
> from this code", but generally the unit of C is J/(mol.K). For example, 
> for a ABX3 compound, if the unit cell contains 30 atoms (A:6, B:6, 
> X:18), the calculated C (J/(mol-c.K) from this code must be divided by 
> 30 in order to transfer to the general expression C (J/(mol.K). Is it 
> right?

No: 30 is the number of atoms. If you want "per mol" you have to divide by 
the number of formula units in the unit cell, which is 6 in your case. If 
you want "per gram" you divide by the number of grams in a mol of your 
unit cell (with all 30 atoms) so 
6*atomicweight(A)+6*atomicweight(B)+18*atomicweight(X)

where, e.g., atomicweight(carbon) = 12 g.

Matthieu

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Dr. Matthieu Verstraete                 mailto:mjv500@york.ac.uk
Dept. of Physics, University of York,     tel: +44 1904 43 22 08
Heslington, YO10 5DD York, United Kingdom fax: +44 1904 43 22 14