Computational Chemistry

a frequency calculation are usually not needed, since the semiempirical energy is normally not adjusted by adding the ZPE (Secti ...

All the normal modes are present in the results of a semiempirical frequency calculation, as is the case for an ab initio or DFT ...

6.3.4 Properties Arising from Electron Distribution: Dipole Moments, Charges, Bond Orders The discussion in Section5.5.4on dipol ...

6.3.4.1 Dipole Moments Hehre’s extensive survey of practical computational methods reports the results of ab initio and DFT sing ...

[ 88 , 107 ] dipole moments for ten molecules, using these methods: AM1 (using the AM1 method to calculatemfor the AM1 geometry, ...

molecules gave mean absolute errors of: AM1, 0.35 D and PM3, 0.38 D [ 70 ]. So with these larger samples the AM1 errors were som ...

propenal). Consider first Mulliken charges and bond orders of the enolate (Fig.6.9a). The AM1 and PM3 charges, which are essenti ...

The Mulliken charges of the protonated enone system (Fig.6.9b) make the oxy- gen negative, which may seem surprising. However, t ...

spectra, and ionization energies (ionization potentials) and electron affinities will be discussed here. 6.3.5.1 UV Spectra As p ...

values [ 115 , 116 ], for the molecules of Table5.17. This admittedly very small sample suggests that semiempirical IEs calculat ...

HOMO localized on one atom, the error was 1.40 eV [ 117 ]. The errors from AM1 or PM3 should be less than for these MNDO calcula ...

6.3.7 Some General Remarks.......................................... AM1 and PM3 have become extremely useful not only because t ...

ironically, these journals have no such reservations against density functional theory (Chapter 7), despite its significant semi ...

structures; PM3 has been reported to tend to give more reliable structures, and AM1 better energies [ 110 ]. Neither AM1 nor PM3 ...

AM1 and PM3 perform similarly and usually give quite good geometries, but less satisfactory heats of formation and relative ener ...

(a) Wilson E (1998) Chem Eng News October 19:12; (b) Malakoff D (1998) Science 282:610; (c) Nobel lecture: Angew Chem Int Ed (1 ...

Spartan is an integrated molecular mechanics, ab initio and semiempirical program with an input/output graphical interface. It ...

http://www.cache.fujitsu.com/mopac/Mopac2002manual/node650.html Stewart JJP (2007) J Mol Model 13:1173 http://openmopac.net/MOP ...

latter. Bettinger et al., 1997 (above) calculate the barrier to be 21 kJ mol"^1 (5 kcal mol"^1 ). The G3MP2 method places the ga ...

(a) Leach AR (2001) Molecular modelling, 2nd edn. Prentice Hall, Essex, England, chapter 12; (b) H€oltje H-D, Folkers G (1996) ...