From the Four-Orbital Model to the Three-Orbital Model: Parameterizing the Qx/Qy-Band Energies in Phthalocyanines and Their Analogues Using Symmetry-Adapted Perturbation Theory.

Contribution of the HF (Hartree-Fock) Method to Predicting the First Reduction Potential of TCNQ (Tetracyanoquinodimethane) Derivatives: A Comparative Study with the DFT (Density Functional Theory) Method

This investigation examined whether the first reduction potential of forty (40) Tetracyanoquinodimethane (TCNQ) derivatives could be described using a single quantum-chemical descriptor. Molecular geometries were optimised and frequency calculations were undertaken at the HF/6-31G(d,p) level of theory. Electron affinit...

Validating orbital-optimized linearized coupled-cluster theory for high-accuracy thermochemistry and spectroscopy of prototypical π-systems: Ethylene and its ions.

High-level ab initio estimates for the equilibrium structure (rCC = 1.330 79 ± 0.000 31 Å, rCH = 1.080 75 ± 0.000 21 Å, and αCCH = 121.423° ± 0.023°), the adiabatic ionization energy (10.52 eV), and the 0 K proton affinity (673.2 kJ/mol) of ethylene were obtained via focal-point extrapolation of coupled cluster results...

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MR-CISD investigation (including extensivity corrections) of Rydberg n-3 s and n-3p states of the smallest ionized HCl-water cluster

The [H3O(H2O)3]+Cl− ion-pair is the smallest cluster of ionized HCl in water. It has been demonstrated experimentally that it can be formed in conditions compatible with the interstellar medium (ISM). It is also a precursor of another ion-pair, H3O+(MetOH)3Cl−, suggested as an important prebiotic species in the ISM. Ai...

Using energy decomposition analysis from correlated wavefunction theory to characterize a range of hydrogen, halogen, and tetrel bonds: the relative importance of electrostatics, charge-transfer and polarization.

Second-order Møller-Plesset theory (MP2) is the simplest wavefunction-based treatment of electron correlation and is a good compromise between accuracy and efficiency for evaluating the strength of many non-covalent intermolecular interactions. It has also been improved in accuracy and robustness by regularized methods...

Benchmark MRCI Study of Halogen Oxides: Potential Energy Surfaces and Spectroscopic Constants for X2, XO, and X2O (X = F, Cl, Br)

High-level quantum chemical methods (MRCI+Q and MRCI+P) combined with large correlation-consistent basis sets (aug-cc-pVnZ, where n = Q, 5, 6), were used to investigate the ground-state potential energy curves (PECs) and surfaces (PESs) of the X2, XO, and X2O systems (with X = F, Cl, Br). For the triatomic systems, the...