just to add again on thuis issue: Some (most?) anions have positive homo energies. I suppose this means they do not really exist in isolation. I wonder what the correct way of calculating the energis in solution for such species would be. I was thinking of I want to calculate the energy of an anionic species, A-(aq), then I can consider the cycle:

AH = A-(aq) +H+(aq). Both AH (which is neutral) and H+ obviously hav epositive homos and so can be considered stable, so E(AH-H+(aq)) can be considered the true energy of A- in solution, and it may/may not differ from a direct calculation of a hypothetical A- in solution. But then, the energy of A- can easily depend on the nature of the counterion. Is that not a true picture of reality, i.e. energy of an anion in solution should depend on the nature of the surounding cation (even if it is not strongly bound)?

I hope the argument that species with positive HOMOs (think HF energies to avoid the issue of meaning of DFT orbitals) do not exist is true irrespective of the belief about whether orbitals are reality or not (i do not want to re-start that debate).

Noko

-----Original Message-----
From: nokophala##aim.com <owner-chemistry++ccl.net>
To: Phala, Noko <nokophala++aim.com>
Sent: Tue, 7 Feb 2006 14:51:45 -0500
Subject: CCL: Aquous electrochemistry

Sent to CCL by: nokophala-$-aim.com

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Content-Type: text/plain; charset="us-ascii"

Thanks for responses so far, everyone. From my current calcs it does seem that 
one must have the correct structure of the first shell, especially for cationic 
ions. For H+ is is almost mandatory, but already a single water molecules brings 
the solvation energy to within an eV of the correct value. Anionic species seem 
ok'yish even without a shell.  
 



Dr Noko Phala
E-mail: nokophala ~~ aim.com

 
 
-----Original Message-----
> From: Goedele Roos groos[]vub.ac.be <owner-chemistry ~~ ccl.net>
To: Phala, Noko  <nokophala ~~ aim.com>
Sent: Mon, 6 Feb 2006 14:54:03 -0500
Subject: CCL: Aquous electrochemistry


Sent to CCL by: Goedele Roos [groos^-^vub.ac.be]

Yes, the first solvatation shell is important,
see Uudsemaa, M., Tamm, T., J. Phys. Chem. A 2003, 107, 9997.
or see: M. Namazian, Siahrostami, s., Noorbala, M. R., Coote, m. L., J. Mol. 
Struct.: Theochem, 759,(2006), 245.
or: Shamsipur, M., Alizadeh, Arshadi, S., J. Mol. Struct.: Theochem, 758, 
(2005), 71

also a very good paper Dutton, A., S., Fukuto, J. M., Kendall, N. H., J. Inorg. 
Chem. 2005, 44, 4024.

Baik, M.-H., Friesner, A. J. Phys. Chem. A 2002, 106, 7407.

Patterson, E, Cramer, C., Truhlar, D, JACS, 123 (2001) 2025.


Greetz, Goedele

>Sent to CCL by: "Jim Kress" [ccl_nospam#kressworks.com]
>Here's an interesting link:
>
>http://comp.chem.umn.edu/netstep/2000/february/9truhcram.html
>
>
>Jim 
>
>> -----Original Message-----
>> From: nokophala. ~ .aim.com [mailto:owner-chemistry ~ ccl.net] 
>> Sent: Sunday, February 05, 2006 10:22 AM
>> To: Kress, Jim 
>> Subject: CCL: Aquous electrochemistry
>> 
>> Sent to CCL by: nokophala++aim.com
>> 
>> Hi There,
>> Is anyone aware of successes in reproducing some of the 
>> tabulated redox potentials of electrochemical reactions that 
>> ar elisted i standard electrochemical tables, especiall those 
>> involving single ions? e.g. Cu 
>> --> Cu2+(aq) + 2e-. The key issue that I need coment on here is the
>> selection of appropriate solvation models. I doubt if 
>> continuum models would require inclusion of at least the 
>> first shell of water molecules, as these are strongly bound. 
>> As a starting point I am trying to reproduce the experimental 
>> value of the 'reference' reaction 2H+ +2e = H2. Even this 
>> appears tricky.
>> 
>> Thanks in advance,
>> 
>> Noko Phala, Anglo Research
>> ______________________________________________________________
>> __________
>> Check Out the new free AIM(R) Mail -- 2 GB of storage and 
>> industry-leading spam and email virus protection.
>> 
>> 
>> 
>> -= This is automatically added to each message by the mailing 
>> script =-
>> To recover the email address of the author of the message, 
>> please change> Conferences: 
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>> 
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>> Password: search)> 
>> -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>> -+-+-+-+-+>
>
>
>

Drs. Goedele Roos
Dienst Algemene Chemie (ALGC)
Vrije Universiteit Brussel (VUB)
Pleinlaan 2
B-1050 Brussels
Tel: 0032-2-629 35 16
Fax: 0032-2-629 33 17http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp://www.ccl.net/chemistry/sub_unsub.shtmlhttp://www.ccl.net/spammers.txt________________________________________________________________________
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<HTML><BODY><DIV style='font-family: "Verdana"; font-size: 10pt;'><DIV>
<DIV>Thanks for responses so far, everyone. From my current calcs it does seem 
that one must have the correct structure of the first shell, especially for 
cationic ions. For H+ is is almost mandatory, but already a single water 
molecules brings the solvation energy to within an eV of the correct value. 
Anionic species seem ok'yish even without a shell.  </DIV>
<DIV> </DIV>
<DIV><BR><BR><BR>Dr Noko Phala<BR>E-mail: nokophala ~~ aim.com<BR></DIV>
<DIV> </DIV> <BR>-----Original Message-----<BR>From: Goedele Roos 
groos[]vub.ac.be <owner-chemistry ~~ ccl.net><BR>To: Phala, Noko  <nokophala ~~ 
aim.com><BR>Sent: Mon, 6 Feb 2006 14:54:03 -0500<BR>Subject: CCL: Aquous 
electrochemistry<BR><BR>
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<DIV class=AOLPlainTextBody id=AOLMsgPart_0_5b1d94a5-e3d2-4048-b182-b236a00316f8><PRE><TT>Sent 
to CCL by: Goedele Roos [groos^-^vub.ac.be]

Yes, the first solvatation shell is important,
see Uudsemaa, M., Tamm, T., J. Phys. Chem. A 2003, 107, 9997.
or see: M. Namazian, Siahrostami, s., Noorbala, M. R., Coote, m. L., J. Mol. 
Struct.: Theochem, 759,(2006), 245.
or: Shamsipur, M., Alizadeh, Arshadi, S., J. Mol. Struct.: Theochem, 758, 
(2005), 71

also a very good paper Dutton, A., S., Fukuto, J. M., Kendall, N. H., J. Inorg. 
Chem. 2005, 44, 4024.

Baik, M.-H., Friesner, A. J. Phys. Chem. A 2002, 106, 7407.

Patterson, E, Cramer, C., Truhlar, D, JACS, 123 (2001) 2025.


Greetz, Goedele

>Sent to CCL by: "Jim Kress" [ccl_nospam#kressworks.com]
>Here's an interesting link:
>
><A href="http://comp.chem.umn.edu/netstep/2000/february/9truhcram.html" 
target=_blank>http://comp.chem.umn.edu/netstep/2000/february/9truhcram.html</A>
>
>
>Jim 
>
>> -----Original Message-----
>> From: nokophala. ~ .aim.com [<A href="mailto:owner-chemistry">mailto:owner-chemistry</A> 
~ ccl.net] 
>> Sent: Sunday, February 05, 2006 10:22 AM
>> To: Kress, Jim 
>> Subject: CCL: Aquous electrochemistry
>> 
>> Sent to CCL by: nokophala++aim.com
>> 
>> Hi There,
>> Is anyone aware of successes in reproducing some of the 
>> tabulated redox potentials of electrochemical reactions that 
>> ar elisted i standard electrochemical tables, especiall those 
>> involving single ions? e.g. Cu 
>> --> Cu2+(aq) + 2e-. The key issue that I need coment on here is the
>> selection of appropriate solvation models. I doubt if 
>> continuum models would require inclusion of at least the 
>> first shell of water molecules, as these are strongly bound. 
>> As a starting point I am trying to reproduce the experimental 
>> value of the 'reference' reaction 2H+ +2e = H2. Even this 
>> appears tricky.
>> 
>> Thanks in advance,
>> 
>> Noko Phala, Anglo Research
>> ______________________________________________________________
>> __________
>> Check Out the new free AIM(R) Mail -- 2 GB of storage and 
>> industry-leading spam and email virus protection.
>> 
>> 
>> 
>> -= This is automatically added to each message by the mailing 
>> script =-
>> To recover the email address of the author of the message, 
>> please change> Conferences: 
>> <A href="http://server.ccl.net/chemistry/announcements/conferences/" 
target=_blank>http://server.ccl.net/chemistry/announcements/conferences/</A>
>> 
>> Search Messages: <A href="http://www.ccl.net/htdig" target=_blank>http://www.ccl.net/htdig</A>  
(login: ccl, 
>> Password: search)> 
>> -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>> -+-+-+-+-+>
>
>
>

Drs. Goedele Roos
Dienst Algemene Chemie (ALGC)
Vrije Universiteit Brussel (VUB)
Pleinlaan 2
B-1050 Brussels
Tel: 0032-2-629 35 16
Fax: 0032-2-629 33 17E-mail to subscribers: <A href="mailto:CHEMISTRY%40ccl.net">CHEMISTRY 
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