CCL: Computing AsMe3
- From: John McKelvey <jmmckel_+_gmail.com>
- Subject: CCL: Computing AsMe3
- Date: Mon, 4 Oct 2010 12:54:10 -0400
Sent to CCL by: John McKelvey [jmmckel * gmail.com]
PM6 gives 5.14085 Kcal/Mol
John
On Mon, Oct 4, 2010 at 9:30 AM, John McKelvey <jmmckel=gmail.com> wrote:
> It would be interesting to see what PM6 results would be.
>
> John McKelvey
>
> On Mon, Oct 4, 2010 at 7:13 AM, Gerald Knizia
> knizia|,|theochem.uni-stuttgart.de <owner-chemistry=ccl.net> wrote:
>>
>> Sent to CCL by: Gerald Knizia [knizia---theochem.uni-stuttgart.de]
>> On Monday 04 October 2010 11:51, osama T Akoubeh dolkeen(_)hotmail.com
wrote:
>>> I computed the compound AsMe3 " As(CH3)3 " using PM5 and
many functional
>>> methods to get the enthalpy of formation , entropy at various
temperature
>>> to study its behavior reaction [..]
>>>
>>> The value from Chemkin data base is 2,9kcal/mol , the difference
between
>>> both will make the reaction Gibbs favorable at 2.8 and not at 2.9
kcal/mol
>>>
>>> I computed the compound using PM5 methaod anf got 3.2118 kcal/mol
what
>>> functional method you suggest to get 2.8 even I tested B88-PW91
with no
>>> good results
>>
>> This kind of accuracy is far beyond what you could possibly expect from
any
>> DFT or semiempirical method. In fact, I doubt that there currently are
any
>> computational methods capable of achieving this kind of accuracy for
this
>> system, not even for the electronic part alone.
>> The least you'd need to even get reliably into the 1kJ/mol
accuracy range
>> is a compound method (like W4 or HEAT) which includes at least a
CCSDT(Q)
>> calculation and additionally a F12 or CBS[45] (better CBS[56])
calculation of
>> the CCSD(T) basis set limit. My patience would certainly not be
sufficient to
>> do a CCSDT(Q) calculation on such a system.
>> --
>> Gerald Knizia>> http://www.ccl.net/cgi-bin/ccl/send_ccl_message>>
http://www.ccl.net/cgi-bin/ccl/send_ccl_message>>
http://www.ccl.net/chemistry/sub_unsub.shtml>>
http://www.ccl.net/spammers.txt>>
>>
>>
>
>
>
> --
> John McKelvey
> 10819 Middleford Pl
> Ft Wayne, IN 46818
> 260-489-2160
> jmmckel=gmail.com
>
--
John McKelvey
10819 Middleford Pl
Ft Wayne, IN 46818
260-489-2160
jmmckel=gmail.com