Improved atom equivalents method for converting density functional theory energies calculated on molecular mechanics structures to heats of formation

Duchowicz, Pablo R.; Castro, Eduardo A.

doi:10.3998/ark.5550190.0002.115

Cited by 4 publications

(2 citation statements)

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“…Beyond AE schemes, a number of alternatives have been introduced to convert HF or DFT energies into formation enthalpies while correcting their main deficiencies. , These methods focus on neutral molecules and rely on empirical relationships. However, simpler procedures based on eq are not necessarily less reliable. , In favorable situations, they yield average absolute deviations (AAD) from experimental results close to 2.5 kcal/mol. , Therefore, all models considered in the present work rely on eq .…”

Section: Methodsmentioning

confidence: 99%

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Formation Enthalpies of Ions: Routine Prediction Using Atom Equivalents

Mathieu

Pipeau

2010

J. Chem. Theory Comput.

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In view of identifying routine procedures to estimate formation enthalpies of ionic systems such as energetic salts or ionic liquids on the basis of density functional theory (DFT), various combinations of atom equivalent (AE) schemes, functionals, and basis sets are compared, using a specially designed training set to parametrize the models. After correction, none of the functionals considered proves significantly more reliable than B3LYP. A small but systematic improvement is noted as AE values are allowed to depend on the atomic environment. However, AE parameters fail to make up for basis set limitations, in constrast to previous observations for neutrals. Finally, a good trade-off between reliability and cost is obtained for ions using B3LYP/6-31++G** energies.

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Section: Methodsmentioning

confidence: 99%

“…Beyond AE schemes, a number of alternatives have been introduced to convert HF or DFT energies into formation enthalpies while correcting their main deficiencies. 27,28 These methods focus on neutral molecules and rely on empirical relationships. However, simpler procedures based on eq 7 are not necessarily less reliable.…”

Section: Methodsmentioning

confidence: 99%

Formation Enthalpies of Ions: Routine Prediction Using Atom Equivalents

Mathieu

Pipeau

2010

J. Chem. Theory Comput.

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QSPR Modeling of Gibbs Free Energy of Organic Compounds by Weighting of Nearest Neighboring Codes

et al. 2005

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We examine the encoding of chemical structure of organic compounds by Labeled Hydrogen-Filled Graphs (LHFGs). Quantitative Structure-Property Relationships (QSPR) for a representative set of 150 organic molecules have been derived by means of the optimization of correlation weights of local invariants of the LHFGs. We have tested as local invariants Morgan extended connectivity of zero-and first order, numbers of path of length 2 (P2) and valence shells of distance of 2 (S2) associated with each atom in the molecular structure, and the Nearest Neighboring Codes (NNC). The best statistical characteristics for the Gibbs free energy has been obtained for the NNC weighting. Statistical parameters corresponding to this model are the following n = 100, r 2 = 0.9974, s = 5.136 kJ/mol, F = 38319 (training set); n = 50, r 2 = 0.9990, s = 3.405 kJ/mol, F = 48717 (test set). Some possible further developments are pointed out.

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