>>>> or should i be doing < U+<V>*ref_p > = <H>?
>>
>>> More specifically, <U> + <V>*ref_p = H
>>
>>> <H> isn't really meaningful thing. I mean, you can define something
>>> such that <H*> = H, but that's not really thermodynamics.
>>
>> sorry I always have issues deciding how to talk about this stuff, so
>> thanks
>> for putting up with my terrible notation =)
>>
>>>> example system gives <H> = -1168 kJ/mol and i find <H> = -725 kJ/mol
>>>> either
>>
>>> Interesting. What material at what phase conditions? For liquids,
>>> the PV contribution should be very small.
>>
>> I hadn't really thought about that... but the system is a monatomic
>> Lennard-Jones particle (uncharged sigma = 0.35 nm epsilon = 2 kJ/mol mass
>> =
>> 40 amu) which should be a liquid at the conditions I was looking at,
>> P=1000
>> bar, T = 300 K using phase diagram in: Equation of state for the
>> Lennard-Jones fluid, J. J. Nicolas et al., MOLECULAR PHYSICS, 1979, VOL.
>> 37,
>> No. 5, 1429-1454
>>
>> the <U> is -1600 and the p<V> is 880 when manually done, around 400 from
>> g_energy
>Here's the code:
> /* This is pV (in kJ/mol). The pressure is the reference
> pressure,
> not the instantaneous pressure */
> pv = vol*md->ref_p/PRESFAC;
>
> add_ebin(md->ebin, md->ipv, 1, &pv, bSum);
> enthalpy = pv + enerd->term[F_ETOT];
>
>What is your volume?
>What is Etot?
a bit messy but this is data from g_energy for the system with increasing
temperature (300 K-1000 K), and constant pressure of 1000 bar (so 100 000
000 Pascals):
Temperature Volume Enthalpy Potential Total Energy pV
Kinetic En.
K nm^3 kJ/mol kJ/mol
kJ/mol kJ/mol kJ/mol
299.914 14.7226 -1168.83 -2565.44 -1611.63 442.791
953.817
399.901 17.462 -339.795 -2080.31 -808.501 468.706
1271.81
499.898 21.0263 421.763 -1666.7 -76.8794 498.643
1589.83
599.899 25.1149 1088.79 -1348.14 559.718 529.07
1907.86
699.914 29.4219 1668.2 -1115.47 1110.46 557.733
2225.94
799.925 33.764 2184.31 -943.613 1600.39 583.922
2544
899.923 38.0865 2660.3 -809.572 2052.45 607.847
2862.03
999.931 42.2798 3101.56 -707.908 2472.17 629.383
3180.08
all uncorrected for the number of particles in the box (so Etot is in kJ/256
mol of particles)
when i use this data to get H myself i get:
H
kJ/mol
-725.32948
242.7114
1188.90386
2071.63498
2881.65838
3632.9828
4345.2573
5017.41396
again uncorrected for the number of particles in the box
Thoughts?
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