Additivity Rules for the Ab Initio Interaction Energy of a Cluster Using the Results of Different Smaller Basis Sets

2000 ◽  
pp. 69-72
Author(s):  
J. G. C. M. Duijneveldt-van de Rijdt ◽  
F. B. Duijneveldt
Keyword(s):  
Ab Initio ◽  
Interaction Energy ◽  
Basis Sets ◽  
Additivity Rules

Carbonyl–Carbonyl Interactions can be Competitive with Hydrogen Bonds

1998 ◽  
Vol 54 (3) ◽  
pp. 320-329 ◽  
Author(s):  
F. H. Allen ◽  
C. A. Baalham ◽  
J. P. M. Lommerse ◽  
P. R. Raithby
Keyword(s):  
Hydrogen Bonds ◽  
Ab Initio ◽  
Interaction Energy ◽  
Molecular Orbital ◽  
Crystallographic Data ◽  
Basis Sets ◽  
Attractive Interaction ◽  
Molecular Orbital Calculations ◽  
Dimer Model ◽  
Intermolecular Perturbation Theory

The geometries and attractive energies of carbonyl–carbonyl interactions have been investigated using crystallographic data and ab initio molecular-orbital calculations. Analysis of crystallographic data for 9049 carbon-substituted >C=O groups shows that 1328 (15%) form contacts with other >C=O groups, in which d(C...O) < 3.6 Å. Three common interaction motifs are observed in crystal structures: (a) a slightly sheared antiparallel motif (650 instances) involving a pair of short C...O interactions, together with (b) a perpendicular motif (116 instances) and (c) a highly sheared parallel motif (130 instances), which both involve a single short C...O interaction. Together, these motifs account for 945 (71%) of the observed interactions. Ab-initio-based molecular-orbital calculations (6-31G** basis sets), using intermolecular perturbation theory (IMPT) applied to a bis-propanone dimer model, yield an attractive interaction energy of −22.3 kJ mol−1 for a perfect rectangular antiparallel dimer having both d(C...O) = 3.02 Å and attractive energies < −20 kJ mol−1 over the d(C...O) range 2.92–3.32 Å. These energies are comparable to those of medium-strength hydrogen bonds. The IMPT calculations indicate a slight shearing of the antiparallel motif with increasing d(C...O). For the perpendicular motif, IMPT yields an attractive interaction energy of −7.6 kJ mol−1, comparable in strength to a C—H...O hydrogen bond and with the single d(C...O) again at 3.02 Å.

A Systematic DFT Study of Two Elementary Steps Involving Hydrogen Peroxide and the Hydroxyl Radical in the Fenton Reaction

2018 ◽  
Author(s):  
Danilo Carmona ◽  
David Contreras ◽  
Oscar A. Douglas-Gallardo ◽  
Stefan Vogt-Geisse ◽  
Pablo Jaque ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Hydroxyl Radical ◽  
Ab Initio ◽  
Fenton Reaction ◽  
Basis Set ◽  
Basis Sets ◽  
Dft Methods ◽  
Elementary Steps ◽  
Oxygen Oxygen ◽  
Complete Basis Set

The Fenton reaction plays a central role in many chemical and biological processes and has various applications as e.g. water remediation. The reaction consists of the iron-catalyzed homolytic cleavage of the oxygen-oxygen bond in the hydrogen peroxide molecule and the reduction of the hydroxyl radical. Here, we study these two elementary steps with high-level ab-initio calculations at the complete basis set limit and address the performance of different DFT methods following a specific classification based on the Jacob´s ladder in combination with various Pople's basis sets. Ab-initio calculations at the complete basis set limit are in agreement to experimental reference data and identified a significant contribution of the electron correlation energy to the bond dissociation energy (BDE) of the oxygen-oxygen bond in hydrogen peroxide and the electron affinity (EA) of the hydroxyl radical. The studied DFT methods were able to reproduce the ab-initio reference values, although no functional was particularly better for both reactions. The inclusion of HF exchange in the DFT functionals lead in most cases to larger deviations, which might be related to the poor description of the two reactions by the HF method. Considering the computational cost, DFT methods provide better BDE and EA values than HF and post--HF methods with an almost MP2 or CCSD level of accuracy. However, no systematic general prediction of the error based on the employed functional could be established and no systematic improvement with increasing the size in the Pople's basis set was found, although for BDE values certain systematic basis set dependence was observed. Moreover, the quality of the hydrogen peroxide, hydroxyl radical and hydroxyl anion structures obtained from these functionals was compared to experimental reference data. In general, bond lengths were well reproduced and the error in the angles were between one and two degrees with some systematic trend with the basis sets. From our results we conclude that DFT methods present a computationally less expensive alternative to describe the two elementary steps of the Fenton reaction. However, choice of approximated functionals and basis sets must be carefully done and the provided benchmark allows a systematic validation of the electronic structure method to be employed

Sodium Interaction with Disodium Terephthalate Molecule: an Ab Initio Study

MRS Advances ◽  
2016 ◽  
Vol 1 (53) ◽  
pp. 3579-3584 ◽  
Author(s):  
Mahasin Alam Sk ◽  
Sergei Manzhos
Keyword(s):  
Ab Initio ◽  
Interaction Energy ◽  
Terephthalic Acid ◽  
Disodium Salt ◽  
Ab Initio Study ◽  
Binding Mechanism ◽  
Carboxylate Groups ◽  
Organic Electrode ◽  
Occupied Orbital ◽  
Electron Occupation

ABSTRACTDisodium terephthalate (Na2TP), which is a disodium salt of terephthalic acid, is very promising organic electrode material for Na-ion batteries. We present an ab initio study of Na binding mechanism with Na2TP molecule. Specially, we provide the interaction energy of Na atom(s), effect of Na concentration on interaction energy, electronic properties of clean and Na attached Na2TP, and Na binding mechanism with Na2TP. We show that up to eight Na atoms can be attached to a single Na2TP molecule. The interaction energy of Na atoms varies from -0.79 to -0.66 eV with attachment of one to eight Na atoms. The adsorbed Na atom interacts with O atoms of carboxylate group and Na atoms of the salt molecule. The interaction between adsorbed Na and C atoms of the molecule is found to be not important for Na bindings. Attachment of a single Na atom generates a singly occupied orbital which becomes doubly occupied with attachment of second Na atoms. Attachment of more than two Na atoms leads to electron occupation of bonding orbitals formed between Na atoms and the carboxylate groups.

scholarly journals Particularly strong C–H⋯π interactions between benzene and all-cis 1,2,3,4,5,6-hexafluorocyclohexane

2015 ◽  
Vol 17 (44) ◽  
pp. 29475-29478 ◽  
Author(s):  
Rodrigo A. Cormanich ◽  
Neil S. Keddie ◽  
Roberto Rittner ◽  
David O'Hagan ◽  
Michael Bühl
Keyword(s):  
Ab Initio ◽  
Interaction Energy ◽  
Benzene Molecule ◽  
Π Interactions ◽  
High Level

According to high-level ab initio results (SCS-MP2/CBS), the interaction energy between all-cis 1,2,3,4,5,6-hexafluorocyclohexane and a benzene molecule is at least −6 kcal mol−1, remarkably large for C–H⋯π interactions between hydrocarbons.

Quantum-Chemical Ab Initio Calculations on Inda- and Thallabenzene (C5H5In and C5H5Tl) and their Structural Isomers η5-C5H5In and η5-C5H5Tl

2018 ◽  
Vol 71 (3) ◽  
pp. 102
Author(s):  
Emma Persoon ◽  
Yuekui Wang ◽  
Gerhard Raabe
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Density Functional ◽  
Single Point ◽  
Normal Modes ◽  
Dft Method ◽  
Basis Sets ◽  
Triplet States ◽  
Structural Isomers ◽  
Td Dft

Quantum-chemical ab initio, time-independent, as well as time-dependent density functional theory (TD-DFT) calculations were performed on the so far elusive heterocycles inda- and thallabenzene (C5H5In and C5H5Tl), employing several different methods (MP2, CISD, CCSD, CCSD(T), BD, BD(T), QCISD, QCISD(T), CASSCF, DFT/B3LYP), effective core potentials, and different basis sets. While calculations on the MP2 level predict the ground states of the title compounds to be singlets with the first triplet states between 13 and 15 kcal mol−1 higher in energy, single point calculations with the QCISD(T), CCSD(T), and BD(T) methods at CCSD-optimized structures result in energy differences between the singlet and the triplet states in the range between 0.3 and 2.1 kcal mol−1 in favour of the triplet states. According to a CASSCF(8,8) calculation the triplets are also more stable by about 2.5–2.9 kcal mol−1. Calculations were also performed for the C5v-symmetric η5 structural isomers (cyclopentadienylindium, CpIn, and cyclopentadienylthallium, CpTl, Cp = C5H5) of the title compounds. At the highest level of theory employed in this study, C5H5In is between 79 and 88 kcal mol−1 higher in energy than CpIn, while this energy difference is even larger for thallabenzene where C5H5Tl is energetically between 94 and 102 kcal mol−1 above CpTl. In addition we report on the UV/vis spectra calculated with a TD-DFT method as well as on the spectra of the normal modes of C5H5In and C5H5Tl. Both types of spectra might facilitate identification of the title compounds eventually formed in photolysis or pyrolysis experiments.

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