CCL: Computing AsMe3



 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>>;
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    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