Relative Performance of Gaussian theories
1) Relative computational effort and accuracy:
L. A. Curtiss, P. C. Redfern, K. Raghavachari, V. Rassolov, J. A. Pople,
"Gaussian-3 theory using reduced Møller-Plesset order"
J. Chem. Phys. 1999, 110, 4703 - 4709.
| Method | Rel. CPUa | MAD(1)b | MAD(2)c
|
|---|
| G3(MP2) | 1.0 | 4.94 | 5.44
|
| G2(MP2) | 2.9 | 8.49 | 7.91
|
| G3 | 7.8 | 3.93 | 4.23
|
| G2 | 14.7 | 6.53 | 6.19
|
a Relative CPU time for benzene (D6h)
b Mean absolute deviation for the extended G2 neutral set (148 energies, kJ/mol)
c Mean absolute deviation for all energies in the extended G2 set (299 energies, kJ/mol)
It is clear from these results that G3 theory is the most accurate method for a broad range of
molecular and atomic systems, while G3(MP2) theory is the most economical method. It must also
be noted that G3(MP2) is more accurate than G2 theory!
2) B3LYP vs. MP2 geometries:
A. G. Baboul, L. A. Curtiss, P. C. Redfern, K. Raghavachari
"Gaussian-3 theory using density functional geometries and zero-point energies"
J. Chem. Phys. 1999, 110, 7650 - 7657.
| Method | MAD(1)a | MAD(2)b
|
|---|
| G3 | 3.93 | 4.26
|
| G3B3 | 3.89 | 4.14
|
| G3(MP2) | 4.94 | 5.44
|
| G3(MP2)B3 | 4.73 | 5.23
|
a Mean absolute deviation for the extended G2 neutral set (148 energies, kJ/mol)
b Mean absolute deviation for the full G2/97 test set (299 energies, kJ/mol)
The use of B3LYP or MP2 geometries does not lead to dramatically different MADs for both
test sets. Especially for large systems, the use of the more economical B3LYP method for geometry
optimization appears to be advisable.
3) Performance in treating open shell systems:
D. J. Henry, M. B. Sullivan, L. Radom,
"G3-RAD and G3X-RAD: Modified Gaussian-3 (G3) and Gaussian-3X (G3X) procedures for radical thermochemistry"
J. Chem. Phys. 2003, 118, 4849 - 4860.
| Method | MADa | LDb | MADc
|
|---|
| G3(MP2) | 5.15 | +11.72 | 5.44
|
| G3(MP2)-RAD | 5.10 | +13.39 | 5.17
|
| G3(MP2)B3 | 4.94 | +13.39 | 5.23
|
| G3 | 3.51 | -7.94 | 4.26
|
| G3-RAD | 3.19 | +12.86 | 3.96
|
| G3B3 | 3.18 | +10.04 | 4.14
|
| G3X | 3.18 | -8.79 | 4.02
|
| G3X-RAD(5d) | 3.14 | +9.14 | 3.85
|
| G3-RAD | 2.59 | +11.01 | 3.96
|
| G3X-RAD | 2.50 | +8.16 | 3.65
|
a Mean absolute deviation for 29 radicals in the G2/97 test set (kJ/mol)
b Largest deviation for 29 radicals in the G2/97 test set (kJ/mol)
c Mean absolute deviation for the full G2/97 test set (kJ/mol)
The differences between the "RAD"-modified procedures and the corresponding references methods
(G3(MP2)-RAD vs. G3(MP2)B3; G3-RAD vs. G3B3; G3X-RAD vs. G3X) are not very large in general.
This may, however, be different for systems involving large, strongly delocalized radicals.
last changes: 01.04.2008, AS
questions & comments to: axel.schulz@uni-rostock.de