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From: "Donald G. Truhlar" <truhlar@umn.edu>
Subject: Re: [NWCHEM] M05-2X
Date: Wed, 14 Feb 2007 10:50:58 -0600
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I agree with some recent comments on density functionals, in  
particular that many density functionals become inaccurate for larger  
systems and are inappropriate for noncovalent interactions.  I note,  
however,  that many of the problems with older DFT functionals have  
been greatly alleviated and even eliminated by the recent M05-2X  
functional.  In particular M05-2X does much better than previous  
functionals on retaining its accuracy for larger systems, and it  
gives excellent results for noncovalent interactions at distances  
important for van der Waals molecules and for conformational  
analysis.  The following references are relevant to these points:

"Design of Density Functionals by Combining the Method of Constraint  
Satisfaction with Parametrization for Thermochemistry, Thermochemical  
Kinetics, and Noncovalent Interactions," Y. Zhao, N. E. Schultz, and  
D. G. Truhlar, Journal of Chemical Theory and Computation 2, 364-382  
(2006).

"Comparative DFT Study of van der Waals Complexes: Rare-Gas Dimers,  
Alkaline-Earth Dimers, Zinc Dimer, and Zinc-Rare-Gas Dimers," Y. Zhao  
and D. G. Truhlar, Journal of Physical Chemistry A 100, 5121-5129  
(2006).

"Assessment of Model Chemistries for Noncovalent Interactions," Y.  
Zhao and D. G. Truhlar, Journal of Chemical Theory and Computation 2,  
1009-1018 (2006).

Density Functionals for Noncovalent Interaction Energies of  
Biological Importance, Y. Zhao and D. G. Truhlar, Journal of  
Chemical Theory and Computation 3, 289-300 (2007).

Assessment of Density Functionals for Pi Systems: Energy Differences  
Between Cumulenes and Poly-ynes and Proton Affinities, Bond Length  
Alternation, and Torsional Potentials of bimoleculgated Polyenes, and  
Proton Affinities of Conjugated Schiff Bases, Y. Zhao and D. G.  
Truhlar, Journal of Physical Chemistry A 110, 10478-10486 (2006).

"Representative Benchmark Suites for Barrier Heights of Diverse  
Reaction Types and Assessment of Electronic Structure Methods for  
Thermochemical Kinetics," J. Zheng, Y. Zhao, and D. G. Truhlar,  
Journal of Chemical Theory and Computation, in press. (available in  
ASAP)

"How Well Can New-Generation Density Functional Methods Describe  
Protonated Epoxides Where Older Functionals Fail?" Y. Zhao and D. G.  
Truhlar, Journal of Organic Chemistry 72,  295-298 (2007).

"A Density Functional Theory that Accounts for Medium-Range  
Correlation Energies in Organic Chemistry," Y. Zhao and D. G.  
Truhlar, Organic Letters 8, 5753-5755 (2006).

"Computational Requirements for Simulating the Structures and Proton  
Activity of Silicaceous Materials." Zhang, Y.; Li, Z. H.; Truhlar, D.  
G. Journal of Chemical Theory and Computation, in press. (available  
in ASAP)

NWChem is the first computer package to release the M05-2X functional.

Don Truhlar
************************************************************************ 
****
Donald G. Truhlar
    truhlar@umn.edu   [editorial: editor@chem.umn.edu]
    http://comp.chem.umn.edu/Truhlar
Regents Professor of Chemistry, Chemical Physics, Nanoparticle
    Science and Engineering, and Scientific Computation
Department of Chemistry, University of Minnesota, 207 Pleasant St. SE,
    Minneapolis, MN 55455   Phone 612-624-7555   Fax 612-626-93900
Secretary:  Flurnia Hadley-Davis  (davis@chem.umn.edu)
************************************************************************ 
***

On Feb 14, 2007, at 9:08 AM, Francesco Pietra wrote:

> --- "Dixon, David" <dadixon@as.ua.edu> wrote:
>
>> One should be careful about all DFT energies. The
>> errors tend to be
>> random and not good to better than +/- 5 kcal/mol
>> for relative energies.
>
> This confirms my problems.
>
>> Total atomization energies are completely different.
>
> What I am also experiencing. Though, working with
> natural products without repeating units, as I do,
> molecules of 50 atoms are small molecules, and total
> atomizations becomes easily problematic. Especially if
> one is involved with conformations, where deltaE may
> be <1 kcal/mol, if one wants to check, before
> attacking the problems of experimentally
> unapproachable conformers. What I am used to do, is
> MP2 single-point energy on dft geometry optimized.
>
>
>> I am not talking
>> about this functional specifically but all DFT
>> functionals in general.
>> It also depends if non-bonding interactions are
>> important.
>
> Non bonding interactions are commonplace with natural
> products.
>
>> DFT is known
>> to get worse the larger the system.
>
> See above.
>
> A question too: What about Car-Parrinello for the
> problems I alluded to above? En plus: Car_Parrinello
> through pseudopotential plane waves?
>
> See above.
>>
>> David
>> David A Dixon
>> Robert Ramsay Chair
>>
>> -----Original Message-----
>> From: owner-nwchem-users@emsl.pnl.gov
>> [mailto:owner-nwchem-users@emsl.pnl.gov] On Behalf
>> Of Francesco Pietra
>> Sent: Wednesday, February 14, 2007 1:18 AM
>> To: users nwchem
>> Subject: [NWCHEM] m05-2x energies at minimum basis
>> set
>>
>> Is it any experience about the reliability of dft
>> energies for small (50 first-row atoms) and large
>> (100
>> first-row atoms) closed-shell geometry-optimized
>> molecules at what was suggested as the minimum basis
>> set (6-31+G*) for the m05-2x functional?
>>
>> Thanks
>> francesco pietra
>>
>>
>>
>>
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