CCL:G: energy for proton
- From: "Alexander Bagaturyants"
<bagaturyants[]gmail.com>
- Subject: CCL:G: energy for proton
- Date: Fri, 13 Apr 2012 12:29:09 +0400
Sent to CCL by: "Alexander Bagaturyants" [bagaturyants%gmail.com]
Dear Thomas,
Of course, a proton can exist as a free particle in vacuum, and you also can
calculate some formal quantities using some standard equations, but (!)
One can never consider a mole of protons in a finite volume or a mole of
protons at a finite pressure, and one can never consider a proton as an
ideal particle.
A free proton can have any possible kinetic energy, but it cannot exist in a
thermodynamic equilibrium and its kinetic energy depends not on the bath
temperature but on conditions of its generation. It cannot be characterized
by a temperature, because temperature relates to an ensemble rather than an
individual particle.
One cannot consider an equilibrium like AH -> A(-) + H(+), and the
equilibrium constant for this reaction makes no sense.
Sorry for these trivial explanations.
PS: I would not like to discuss here de Broglie's concept of hidden
thermodynamics of an isolated particle, because this is a different story.
Best regards
Alexander
> -----Original Message-----
> From: owner-chemistry+sasha==photonics.ru+/-ccl.net [mailto:owner-
> chemistry+sasha==photonics.ru+/-ccl.net] On Behalf Of steinbrt=-
> =rci.rutgers.edu
> Sent: 13 April, 2012 11:25
> To: Alexander Bagaturyants
> Subject: CCL:G: energy for proton
>
>
> Sent to CCL by: steinbrt!A!rci.rutgers.edu Dear CCLers,
>
> I found the most recent comments on this by Alexander suprising. This
> is a particularly interesting discussion thread and I hope someone else
> will comment more on this.
>
> Why would thermodynamic parameters for a proton not make sense? As a
> free particle in vacuum it exists, and for any particle with a mass I
> can compute ideal values for its enthalpy, entropy and temperature
> (well, for one particle, kinetic energy at least).
>
> Moving from a description of a single particle in vacuum to a mol of
> (ideal) particles at standard state is then at least conceptually
> possible.
>
> The fact that a mol of H+ does not exist any more than a mol of Ac-
> doesn't change the fact that I can use it as a reference in computing
> thermodynamic properties of the reaction HAc -> H+ + Ac- from the
> properties of its constituent molecules.
>
> Furthermore, why can a deprotonation reaction not be described by
> thermodynamics? The fragmentation of e.g. HF -> F- + H+ in vacuum will
> have an equilibrium that lies exceptionally far to the left, but at
> high temperature some fragmentation would occur (disregarding the
> alternative radical cleavage for now, which would be more likely but
> shouldn't stop the heterolytic cleavage from happening)
>
> If I am wrong in any of the above, I would be happy to be corrected :-)
>
> Kind Regards,
>
> Thomas
>
> On Thu, April 12, 2012 1:17 pm, Alexander Bagaturyants
> sasha#photonics.ru
> wrote:
> >
> > Sent to CCL by: "Alexander Bagaturyants" [sasha ..
photonics.ru] A
> > good comment by Prof. Sukumar!
> > However, it seems that it was not too straightforward, because some
> > misleading comments still appear and appear.
> > The matter of fact is that neither enthalpy, nor entropy, nor
> > temperature of a free proton makes physical sense. One cannot
> > construct a (thermodynamic) ensemble of free protons. A reaction in
> > which a proton is detached from a molecule can proceed only under
> > nonequilibrium conditions, it is a dynamic rather than thermodynamic
> > process.
> > That is, it senseless to calculate formally any thermodynamic
> function
> > of a free (individual) proton.
> > Hope this will make things a little bit more clear.
> > Best regards
> > Alexander
> >
> >> -----Original Message-----
> >> From: owner-chemistry+sasha==photonics.ru===ccl.net [mailto:owner-
> >> chemistry+sasha==photonics.ru===ccl.net] On Behalf Of N. Sukumar
> >> nagams(a)rpi.edu
> >> Sent: 12 April, 2012 15:27
> >> To: Alexander Bagaturyants
> >> Subject: CCL:G: energy for proton
> >>
> >>
> >> Sent to CCL by: "N. Sukumar" [nagams~~rpi.edu] "Why
not perform the
> >> calculation on proton?"
> >>
> >> This is an interesting philosophical/pedagogical question. My
answer
> >> would be: because for many students (and others), the output from
a
> >> computer is the end of the problem, not the beginning of the
> question!
> >> If the computation is used as an aid to understand the chemistry,
> >> well and good. But many people these days will not believe a
> >> numerical answer unless it is produced by a calculator or a
> computer.
> >> And they may see no need to question those numbers/output any
> further.
> >>
> >> N. Sukumar
> >> Rensselaer Exploratory Center for Cheminformatics Research
Professor
> >> of Chemistry Shiv Nadar University
> >> --------------------------
> >> "When you get exactly the opposite result to what you
predict, you
> >> know it is right, because there is no bias." -- David Nutt,
Imperial
> >> College, London.
> >>
> >> ==============Original message text=============== On Thu, 12 Apr
> >> 2012
> >> 4:13:44 EDT "Peeter Burk peeter.burk^ut.ee" wrote:
> >>
> >>
> >> Sent to CCL by: Peeter Burk [peeter.burk * ut.ee] Why not perform
> the
> >> calculation on prorton? With Gaussian 09 (if I remember correctly,
> >> then with g03 you had to use Freq=NoRaman to get the same results)
> >> you will
> >> get:
> >>
> >> -------------------
> >> - Thermochemistry -
> >> -------------------
> >> Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
> >> Atom 1 has atomic number 1 and mass 1.00783
> >> Molecular mass: 1.00783 amu.
> >> Zero-point vibrational energy 0.0 (Joules/Mol)
> >> 0.00000 (Kcal/Mol)
> >> Vibrational temperatures:
> >> (Kelvin)
> >>
> >> Zero-point correction= 0.000000
> >> (Hartree/Particle)
> >> Thermal correction to Energy= 0.001416
> >> Thermal correction to Enthalpy= 0.002360
> >> Thermal correction to Gibbs Free Energy= -0.010000
> >> Sum of electronic and zero-point Energies= 0.000000
> >> Sum of electronic and thermal Energies= 0.001416
> >> Sum of electronic and thermal Enthalpies= 0.002360
> >> Sum of electronic and thermal Free Energies= -0.010000
> >>
> >>
> >> Peeter Burk
> >> University of Tartu
> >>
> >> On 04/12/2012 10:17 AM, Tymofii Nikolaienko tim_mail*_*ukr.net
> wrote:
> >> >
> >> > Sent to CCL by: Tymofii Nikolaienko [tim_mail{=}ukr.net] Yes,
ZPE
> >> > is zero.
> >> > However, if considering temperatures higher than 0 K, we can
NOT
> >> > neglect the kinetic energy of the proton, since its thermal
> avarage
> >> is
> >> > 3 * kT / 2 !
> >> >
> >> > It is easy to demonstrate if you run the following for
example
> with
> >> > H
> >> atom:
> >> >
> >> > # opt freq b3lyp/aug-cc-pVQZ int=ultrafine
> >> >
> >> > H atom
> >> >
> >> > 0 2
> >> > H 0.0 0.0 0.0
> >> >
> >> > And than you read in the output file:
> >> > ...
> >> > - Thermochemistry -
> >> > -------------------
> >> > Temperature 298.150 Kelvin. Pressure 1.00000 Atm.
> >> > ...
> >> > Zero-point correction= 0.000000 (Hartree/Particle) Thermal
> >> > correction to Energy= 0.001416 Thermal correction to
Enthalpy=
> >> > 0.002360 Thermal correction to Gibbs Free Energy= -0.010654
> >> >
> >> > These thermal corrections would be just that same for the
proton
> >> since
> >> > when calculating thermochemistry Gaussian assumes ground
electron
> >> > state only (so no electronic degrees of freedom contribute to
> >> > thermal corrections; see
> >> > http://www.gaussian.com/g_whitepap/thermo.htm ).> Note
that
> >> > "0.001416" (the "Thermal correction to
Energy") equals 3/2*k*T for
> >> > T = 298.15 K, while "0.002360" (" Thermal
correction to
> >> > Enthalpy") equals 3/2*k*T + k*T since the enthalpy is H
= U + P*v
> >> > while P*v = k*T for ideal gas - the model for calculating
> >> > thermochemistry Gaussian assumes (where v is the gas volume
per
> >> > particle). To obtain Gibbs free energy use the -T*s term
where s
> is
> >> > the entropy of ideal gas per particle at given temperature.
> >> >
> >> > Yours sincerely
> >> > Tymofii Nikolaienko
> >> >
> >> >
> >> > 12.04.2012 8:30, Alexander Bagaturyants
bagaturyants-.-gmail.com
> >> wrote:
> >> >> Sent to CCL by: "Alexander Bagaturyants"
> >> >> [bagaturyants_-_gmail.com] Dear Arturo, Proton has no
internal
> >> >> degrees of freedom; therefore, its energy is zero, if we
neglect
> its kinetic energy.
> >> >> Naturally, the kinetic energy (of a free proton) can take
on any
> >> >> value, so that we may speak about so-called dissociation
> threshold.
> >> >> A piece of advice: when you consider chemistry, you
should not
> >> >> sometimes forget about physics.
> >> >> Best regards
> >> >> Alexander
> >> >>
> >> >>> -----Original Message-----
> >> >>> From: owner-chemistry+sasha==photonics.ru|,|ccl.net
> >> >>> [mailto:owner-
> >> >>> chemistry+sasha==photonics.ru|,|ccl.net] On Behalf Of
Arturo
> >> >>> chemistry+Espinosa
> >> >>> artuesp|*|um.es
> >> >>> Sent: 11 April, 2012 21:12
> >> >>> To: Alexander Bagaturyants
> >> >>> Subject: CCL: energy for proton
> >> >>>
> >> >>>
> >> >>> Sent to CCL by: Arturo Espinosa [artuesp(_)um.es]
Dear CCL
> users:
> >> >>>
> >> >>> I am trying to compute ZPE-corrected dissociation
energies for
> >> >>> some particular bonds, in order to correlate these
values with
> >> >>> other properties computed at the same level (starting
from,
> let's
> >> >>> say,
> >> >>> B3LYP- D/def2-TZVP). My problem (perhaps a bit
stupid) comes
> when
> >> >>> dealing with heterolytic dissociations of a A-H bond
to give A-
> >> >>> (anion) and H+ (a proton). Moreover I am intending to
compare
> >> >>> this dissociation with the other possible heterolytic
> >> >>> dissociation and even with the homolytic one.
Calculation of the
> >> >>> A-H and A- species is straighforward (no matter what
level of
> >> >>> calculation), but the problem is what value (in
atomic
> >> >>> units) should I assign to the H+ species. No QC
calculation is
> >> >>> possible as there are no electrons. I recognize that
I am a bit
> >> lost.
> >> >>> Suggestions are wellcome.
> >> >>> Thank you in advance and best regards,
> >> >>> Arturo> To recover the email address of the author
of the
> >> >>> Arturo> message,
> >> >>> please
> >> >>> change the strange characters on the top line to the
|,| sign.
> >> >>> You can
> >> >>> alsohttp://www.ccl.net/chemistry/sub_unsub.shtmlConferences:>;
> >> >>>
> >> http://server.ccl.net/chemistry/announcements/conferences/http-:-//www
> >> >>> .ccl.net/cgi-
> >> bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/su
> >> >>> b_unsub.shtmlhttp://www.ccl.net/spammers.txt===========End of
> >> >>> original message text===========> To recover the
email address
> of
> >> the author of the message, please
> >> change the strange characters on the top line to the === sign. You
> >> can
> >> also>
> >
> >
>
>
> Dr. Thomas Steinbrecher
> formerly at the
> BioMaps Institute
> Rutgers University
> 610 Taylor Rd.
> Piscataway, NJ 08854> To recover the email address of the author of the
message, please
> change the strange characters on the top line to the +/- sign. You can
> also