[Pw_forum] Total energy of solvated molecules

[Robert Wexler]

Dear QE users,

I just worked example 1 in espresso-5.3.0/Environ/examples/ and obtained
the following result for a water molecule in water solvent:

!    total energy              =     -34.06234148 Ry
     Harris-Foulkes estimate   =     -33.95165940 Ry
     estimated scf accuracy    <          6.8E-12 Ry

     The total energy is the sum of the following terms:

     one-electron contribution =     -81.79999129 Ry
     hartree contribution      =      42.43346037 Ry
     xc contribution           =      -8.39845654 Ry
     ewald contribution        =      13.81332806 Ry
     solvation energy          =      -0.03439636 Ry
     cavitation energy         =       0.01360379 Ry
     PV energy                 =      -0.00691218 Ry

When I sum the energy components, I get -33.97936415 Ry, which is not equal
to the total energy above. I read

O. Andreussi, I. Dabo and N. Marzari, J. Chem. Phys. 136 064102 (2012)

and the authors state that dGsol = dGel + Gcav + *a**S + *b**V + PdV where
*a* and *b* are fitting parameters to reproduce the experimental solvation
energies for a set of reference molecules. Is the "solvation energy" above
the same as dGsol? Is the total energy the sum of these terms or does the
"solvation energy" contain the cavitation and PV energies?

Thanks in advance for your assistance!

Best,
Rob
---------------------------------------------
Robert B. Wexler
PhD Candidate in Chemistry
University of Pennsylvania, 2018
rwexler at sas.upenn.edu
(215) 801-8741
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