Computational Chemistry

deviation from all three calculated results, and because it is among those dihedrals which are said to be suspect or having a la ...

Table 5.7 Errors in HF/3–21G (* ), HF/6–31G*, and MP2(fc)/6–31G* bond lengths and angles, from Fig. 5.23 C–H O–H, N–H, S–H C–C C ...

Table 5.7 (continued) C–H O–H, N–H, S–H C–C C–O, N, F, Cl, S AnglesCH CHCH 2 3 (CCC) 0.4/0.9/0.2MeCl (HCH)0.8/0.5/0.0H S (HSH) 2 ...

although the latter is much faster and often of comparable accuracy (of course with correlated methods like MP2 a smaller basis ...

lengths is only 0.033 A ̊(HF/3–21()level for HCHO) and the largest error in bond angles is only 3.2(HF/3–21()level for H 2 O). ...

indicate them to be minima. The interesting hexaazabenzene (“benzene-N 6 ”) is predicted to be a minimum at the HF/6–31G level, ...

These calculated geometries do not satisfy even our “fairly good” criterion (errors in calculated bond lengths, angles and dihed ...

Ozone is an easier target than FOOF for a high-quality geometry. Some results for this molecule are [ 122 ]: O O O 1.276 1.277 ( ...

and extended H€uckel calculations). We saw that all these energies wererelative to something: that of a species on a potential e ...

mechanical (ab initio, semiempirical, density functional) calculation. In any case, since vibrational calculations are meaningfu ...

constant, is 8.314' 10 #^3 kJ K#^1 mol#^1 and at 298 K,RT¼2.478 kJ mol#^1 and (3/2)RTis 3.717 kJ mol#^1. Thus the internal energ ...

energy” to mean Gibbs free energy. A free energy change can be thought of as an enthalpy change adjusted by a temperature-weight ...

The preexponential factor is tied to the probability of some favorable situation like a propitious collision and involves entrop ...

energy of the electrons, whether calculated by the Hartree–Fock or by a correlation method) plus the internuclear repulsion (cf. ...

(“difference” is defined here as product energy minus reactant energy) governs the extent to which a reaction has progressed at ...

DH¼Hðpdts=TSÞ#Hðreactants) ’Sbond energies(reactants)#Sbond energiesðpdts=TSÞ $ð 5 : 180 Þ (pdt or TS depending on whether we ar ...

DH¼’Sbond energiesðreactantsÞ#Sbond energiesðpdts=TSÞ ¼ð4C#HþC#CþC¼OÞ#ð3C#HþC¼CþC#OþO#HÞ ¼ð 4 ' 414 þ 347 þ 749 Þ#ð 3 ' 414 þ 61 ...

has been strongly criticized [ 144 ], but in the author’s opinion this viewpoint works quite well used pictorially at the molecu ...

is the calculation ofequilibriumconstants from reaction free energies. The crudest way to calculate a rate constant is to use th ...

5.5.2.2 Energies: Calculating Quantities Relevant to Thermodynamics and to Kinetics 5.5.2.2a Thermodynamics; “Direct” Methods; I ...