# mesa-users] dlnP/dlnMu ?

Bill Paxton paxton at kitp.ucsb.edu
Sun May 4 14:13:14 EDT 2008

```The routine eos_get_everything returns all of the HELM results in
addition to the usual mesa/eos results.
In eos_def you'll find a long list of integer parameter definitions
for the results from helm.  The ones starting 'h_dp' are the
derivatives of pressure, and 'h_dpda' is the partial wrt abar,
'h_dpdz' is the partical wrt zbar, etc.

--Bill

On May 4, 2008, at 11:06 AM, Ken Shen wrote:

> That would definitely work, except I don't know how to access dP/d
> (abar)
> etc.  Which function would I use?  There is a dmu/dlnT in the more
> complicated eos_get, but I'm not quite sure what that is...
>
>
> Thanks,
> Ken
>
>
>
> On Sun, 4 May 2008, Frank Timmes wrote:
>
>> hi ken,
>>
>> ok. assuming full ionization,
>>
>> mu_i = 1 /(sum Y_i) = Abar
>>
>> mu_e = 1 /(sum Y_i Z_i) = 1/Y_e
>>
>> mu = ( 1/mu_i + 1/mu_e )**(-1) = 1/(sum Y_i (Z_i + 1)) = Abar/
>> (Zbar + 1)
>>
>> d(mu) = dAbar/(Zbar + 1) + Abar/(Zbar + 1)**2 d(Zbar)
>>
>> the routines return derivatives with respect
>> to composition like dP/d(Abar) and dP/d(Zbar).
>>
>> given the relation between mu, Abar and Zbar
>> can you fill in the rest?
>>
>> fxt
>>
>>
>>
>>> I mean the mean mass per particle, like, 1/mu = 1/mu_i + 1/mu_e.
>>
>>
>>
>

```