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[Display omitted] • Low-lying electronic states of the TM(AcAc) 1-3 (TM = Cr, Fe, Co, Ni, Cu) molecules. • Ligand field theory and CASPT2 electronic structure description. • Cu(AcAc) 1 , Ni(AcAc) 2, and Co(AcAc) 3 molecules present as stability peaks. • Quantitative stability description by the ε3 stability ranking function. Transition metal acetylacetonates have a wide range of technological applications, such as modifiers in polymers and polymerization catalysts. Since the electronic structure defines the physical-chemistry properties of these materials and ultimately their selectivity in technological applications, its characterization is of paramount importance. In this work, the general trends on the electronic structure of the transition metal acetylacetonate TM(AcAc) were estimated from qualitative and quantitative approaches. The qualitative picture, based on the ligand field theory, allowed to establish a relation between the d-orbital electron occupancy and the stability of the system, in which the Cu(AcAc) 2 presents a limitrophe case, indicating moderate stability and reactivity. On the quantitative approach, the low-lying electronic states of TM(AcAc) were characterized by highly correlated methods. The thermodynamic and kinetic stabilities of TM(AcAc) n were ranked by using a stability index based on parameters of the wavefunction, namely, the excitation energy, the free energy of atomization, and the HOMO energy, showing a good agreement with the qualitative results. Besides the spectroscopic data provided for TM(AcAc) n , the combined qualitative and quantitative results can guide the choice of a specific TM(AcAc) n in applications that require higher or lower stabilities. [ABSTRACT FROM AUTHOR]

Abstract: Accurate double ionization energies (DIEs) for low-lying doubly charged states of HCl, HBr, Cl2 and Br2 were calculated using non-relativistic CASSCF/MRCI level of theory with the aug-cc-pVQZ basis set. The results are in excellent agreement with experimental data, presenting absolute average deviations lower than 0.3eV. Some DIEs not previously assigned or well characterized are discussed. Further improvements can be reached by including relativistic effects. [Copyright &y& Elsevier]

Abstract: Geometries, energies, frequencies, and rate constants of the reaction F (2P)+C2H6 →C2H5 +HF were computed using the MP2 and CCSD(T) approaches, correlation-consistent basis sets, and an extrapolation scheme to assess the complete basis set (CBS) limit energies. Values of the enthalpy of reaction at 0K calculated with the CCSD(T)/cc-pVQZ method and extrapolated to the CBS limit are equal to −35.2 and −36.7kcal/mol, respectively (Exp. −35.3±0.5kcal/mol). Rate constants calculated with the zero-order interpolated variational transition state (IVTST-0) method are in good agreement with experiment. [Copyright &y& Elsevier]

Abstract: The effect of constraints on the initial steps of the incorporation of nitrogen on silicon has been assessed by calculations with the [Si9H12 +N] model cluster using density functional theory with the hybrid functional B3LYP, and two basis sets that differ significantly in size. The relative stability of the various stationary points is dependent on the type of constraints imposed on the cluster. Constrained calculations have predicted the structure with the nitrogen symmetrically bonded to the dimer silicons as the global minimum, however, if no constraint is imposed and the whole cluster is optimized, as done in this work, a structure with the nitrogen inserted between the dimer and the first layer and bonded to three silicon atoms is predicted to be the most stable one by about 17kcal/mol by either the doublet or quartet route. The whole process is very exothermic and reaction barriers in the intermediate steps are easily overcome. Calculations with the smaller basis do not essentially change the major conclusion about the relative stability of the various stationary points. The most stable structure and frequency calculations are consistent with a planar NSi3 moiety and its asymmetrical stretching frequency. [Copyright &y& Elsevier]

Abstract: The CH4 +F(2P)→CH3 +HF abstraction reaction was investigated using the BH&HLYP, MP2, and CCSD(T) approaches, and two series of correlation consistent basis sets. At the CCSD(T)/cc-pVTZ level, the classical barrier height (ΔV #), and the vibrationally adiabatic ground-state barrier height () are equal to 1.8 and 0.5kcal/mol, respectively. CCSD(T)/cc-pVQZ calculations give a value for the enthalpy of reaction at 0K () of −31.5kcal/mol (Expt. −32.1kcal/mol). Rate constants calculated with the zero-order interpolated variational transition state (IVTST-0) method are in agreement with experiment. The activation energy computed as local two-points slopes of Arrhenius plots in the temperature range of 200–400K, equal to 0.59kcal/mol, is also in good agreement with experiment (0.53kcal/mol). [Copyright &y& Elsevier]

Abstract: Kinetic isotope effects (KIE) for hydrogen abstraction from CH4, CD4, and 13CH4 by fluorine was studied by the variational transition state theory with multidimensional tunneling contributions (VTST/MT). A low-level potential energy surface is obtained with the AM1SRP method. High-level energies, geometries and frequencies of the reactants, transition state, and products were computed using MP2 and CCSD(T) methods. Using the CVT/μOMT method, the kH/kD kinetic isotope effect value is 1.52 (298K), in excellent agreement with experimental values (1.4–1.5). All computed values of k12C/k13C KIE over a large range of temperatures (200–2000K) show normal values (KIE>1). [Copyright &y& Elsevier]

Electronic energies, geometries, and harmonic vibration frequencies for the reactants, products, and transition state for the Cl(3P)+C2H6→C2H5+HCl abstraction reaction were evaluated at the HF and MP2 levels using several correlation consistent polarized-valence basis sets. Single-point calculations at PMP2, MP4, QCISD(T), and CCSD(T) levels were also carried out. The values of the forward activation energies obtained at the MP4/cc-pVTZ, QCISD(T)/cc-pVTZ, and CCSD(T)/cc-pVTZ levels using the MP2/cc-pVTZ structures are equal to −0.1, −0.4, and −0.3 kcal/mol, respectively. The experimental value is equal to 0.3±0.2 kcal/mol. We found that the MP2/aug-cc-pVTZ adiabatic vibration energy for the reaction (−2.4 kcal/mol) agrees well with the experimental value −(2.2–2.6) kcal/mol. Rate constants calculated with the zeroth-order interpolated variational transition state (IVTST-0) method are in good agreement with experiment. In general, the theoretical rate constants differ from experiment by, at most, a factor of 2.6. [Copyright &y& Elsevier]

Presents corrections to the article, entitled `Energetic and structural features of the CH[sub 4]+O([sup 3]P) CH[sub 3]+OH abstraction reaction: Does perturbation theory from a multiconfiguration reference state (finally) provide a balanced treatment of transition states?,' published in the volume 111 issue of the `Journal of Chemical Physics'.

Abstract: Barrier heights, structures, reaction energies, and rate constants are calculated with the DFT, MP2, and CCSD(T) methods for the first two channels of the H+CH3OH reactions. The best estimate results based on CCSD(T) calculations give reaction enthalpies () for the first (−8.4kcal/mol) and second (0.8kcal/mol) reactive channels, which are comparable to the experimental values, −8.8±0.9 and −0.3±0.9kcal/mol, respectively. Rate constants and activation energies calculated with the IVTST-0 method using CCSD(T)/cc-pVTZ geometries and frequencies are also in excellent agreement with experiment data. [Copyright &y& Elsevier]

Abstract: Geometries, frequencies, energies, and rate constants of the reaction N(4S)+CH4 →NH+CH3 were computed using coupled-cluster theory, correlation-consistent basis sets, and extrapolations schemes to assess the complete basis set limit energies. Our best calculation gives a classical barrier height and reaction energy of 32.9 and 29.3kcal/mol, respectively, and 24.6kcal/mol for the reaction enthalpy (. Thermal (200–2000K) rate constants were calculated with the canonical variational transition state theory, and indicate a very slow reaction when compared with the ones with N(2D) and N(2P). Using the CVT/μOMT method, the value of H/D KIE is 6.3 (300K). [Copyright &y& Elsevier]

Accurate potential energy curves, dissociation energies, and molecular constants for several low-lying singlet and triplet electronic states of AsCl were investigated using the CASSCF/MRCI methodology, including the spin–orbit splitting with the aug-cc-pV5Z-DK basis set. Our results represent an improvement over previous the theoretical descriptions for the lowest lying states, as well as characterize another higher excited state not previously investigated. Transition probabilities and radiative lifetimes for the (1) 3 Π → X 3 Σ − band system were also predicted using Einstein spontaneous emission coefficients. [ABSTRACT FROM AUTHOR]

Highlights: [•] Accurate structures of aluminum clusters: Al n x (n =1–9, x =0, ±1). [•] Electron affinities and ionization potential. [•] DFT and CCSD(T) electronic calculations. [ABSTRACT FROM AUTHOR]

Abstract: The lowest singlet and triplet states of AlP3, GaP3 and BP3 molecules with Cs, C2v and C3v symmetries were characterized using the B3LYP functional and the aug-cc-pVTZ and aug-cc-pVQZ correlated consistent basis sets. Geometrical parameters and vibrational frequencies were calculated and compared to existent experimental and theoretical data. Relative energies were obtained with single point CCSD(T) calculations using the aug-cc-pVTZ, aug-cc-pVQZ and aug-cc-pV5Z basis sets, and then extrapolating to the complete basis set (CBS) limit. [Copyright &y& Elsevier]

Accurate potential energy curves, transition moments, spectroscopic constants, radiative transition probabilities, and lifetimes for the states X 3Σ-, (1) 3Π, and (2) 3Σ- of BeC, MgC, and CaC are reported using high level calculations. Diagonal transitions dominate for the (2) 3Σ- → X 3Σ- system, with band origins falling at 745, 648, and 770 nm, and an intensity ratio of 6,3,1, respectively for BeC, MgC, and CaC. Radiative lifetimes for v′=0 are equal to 0.48, 1.45, and 3.29 μs for the state (2) 3Σ-, and equal to 13.57, 10.44, and 9.62 μs for the state (1) 3Π for BeC, MgC, and CaC. [Copyright &y& Elsevier]