# [Pw_forum] problem to convert Cv (R) to Cv(in J/mol.K)

Stefano de Gironcoli degironc at sissa.it
Thu Feb 2 12:46:56 CET 2012

```Dear Bramha Prasad Pandey,
the question rather seams to me how is it that your phonon DOS
normalization is zero...
this means that the code thinks your system has zero atoms.
stefano

On 02.02.2012 11:40, bramha pandey wrote:
> Sorry to disturbing all of you.
>  But Really i need your's help to understand the the following
> results. Here i am attaching some more information which is obtained
> through the F_QHA.X code.
>
> # Zero vibration energy:      0.0000000005  (Ry/cell)
> # Phonon DOS norm      :      0.000000      ! 3N for check purpose, N
> number of atoms in the unit cell
> # T in K, F_vib in Ry/cell, C_v in R (the universal gas constant by
> 3N
> modes), S in k_B
> #
> #   T         E_internal        F_vibration          Specific heat
> (C_v)       Entropy
>
> ############################################################################################################
>     5.00      0.0000000005      0.0000000005           0.0000000000
>       0.0000000000
>    10.00      0.0000000005      0.0000000005           0.0000000000
>       0.0000000000
>    15.00      0.0000000005      0.0000000005           0.0000000001
>       0.0000000000
>    20.00      0.0000000005      0.0000000005           0.0000000002
>       0.0000000001
>    25.00      0.0000000005      0.0000000005           0.0000000004
>       0.0000000001
>    30.00      0.0000000005      0.0000000005           0.0000000010
>       0.0000000002
>    35.00      0.0000000005      0.0000000005           0.0000000020
>       0.0000000005
>    40.00      0.0000000005      0.0000000005           0.0000000036
>       0.0000000008
>    45.00      0.0000000005      0.0000000005           0.0000000059
>       0.0000000014
>    50.00      0.0000000005      0.0000000005           0.0000000090
>       0.0000000021
>    55.00      0.0000000005      0.0000000005           0.0000000128
>       0.0000000032
>    60.00      0.0000000005      0.0000000005           0.0000000172
>       0.0000000045
>    65.00      0.0000000005      0.0000000005           0.0000000223
>       0.0000000060
>    70.00      0.0000000006      0.0000000005           0.0000000278
>       0.0000000079
>    75.00      0.0000000006      0.0000000005           0.0000000338
>       0.0000000100
>    80.00      0.0000000006      0.0000000005           0.0000000402
>       0.0000000124
>    85.00      0.0000000006      0.0000000005           0.0000000468
>       0.0000000150
>    90.00      0.0000000006      0.0000000005           0.0000000537
>       0.0000000179
>    95.00      0.0000000006      0.0000000005           0.0000000607
>       0.0000000210
>
> Now sir question remain same how i will get the Cv value in J/Mol.K
> from R.?
>
> Your valuable help is needed to me.
>
> On Wed, Feb 1, 2012 at 9:54 PM, bramha pandey
> <pandey.bramha at gmail.com> wrote:
>>
>>
>> Hi..Dear  QE users
>>
>> I have a problem to calculate the Cv value in J/mol.K from Cv(R gas
>> constant). At 300K, the value of Cv is  0.0000002506 . I multiplied
>> 0.0000002506  by 3NR(3*2*8.314) which comes 1.25*10^-5 which was very
>> less compare to experimental Cv value.
>>
>> --
>> Thanks and Regards