scholarly journals N…C and S…S Interactions in Complexes, Molecules, and Transition Structures HN(CH)SX:SCO, for X = F, Cl, NC, CCH, H, and CN

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3232
Author(s):  
Janet E. Del Bene ◽  
Ibon Alkorta ◽  
José Elguero
Keyword(s):  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Second Order ◽  
Binding Energies ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Order Dependence ◽  
Transition Structures ◽  
Bond Charge ◽  
Energy Surfaces

Ab initio Møller–Plesset perturbation theory (MP2)/aug’-cc-pVTZ calculations have been carried out in search of complexes, molecules, and transition structures on HN(CH)SX:SCO potential energy surfaces for X = F, Cl, NC, CCH, H, and CN. Equilibrium complexes on these surfaces have C1 symmetry, but these have binding energies that are no more than 0.5 kJ·mol–1 greater than the corresponding Cs complexes which are vibrationally averaged equilibrium complexes. The binding energies of these span a narrow range and are independent of the N–C distance across the tetrel bond, but they exhibit a second-order dependence on the S–S distance across the chalcogen bond. Charge-transfer interactions stabilize all of these complexes. Only the potential energy surfaces HN(CH)SF:SCO and HN(CH)SCl:SCO have bound molecules that have short covalent N–C bonds and significantly shorter S…S chalcogen bonds compared to the complexes. Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) spin-spin coupling constants 1tJ(N–C) for the HN(CH)SX:SCO complexes are small and exhibit no dependence on the N–C distance, while 1cJ(S–S) exhibit a second-order dependence on the S–S distance, increasing as the S–S distance decreases. Coupling constants 1tJ(N–C) and 1cJ(S–S) as a function of the N–C and S–S distances, respectively, in HN(CH)SF:SCO and HN(CH)SCl:SCO increase in the transition structures and then decrease in the molecules. These changes reflect the changing nature of the N…C and S…S bonds in these two systems.

scholarly journals Perturbing the O–H…O Hydrogen Bond in 1-oxo-3-hydroxy-2-propene

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3086
Author(s):  
Ibon Alkorta ◽  
José Elguero ◽  
Janet E. Del Bene
Keyword(s):  
Potential Energy Surfaces ◽  
Correlation Coefficients ◽  
Binding Energies ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Transition Structures ◽  
Equilibrium Structures ◽  
Acid Potential ◽  
Energy Surfaces ◽  
Spin Spin Coupling

Ab initio MP2/aug’-cc-pVTZ calculations have been carried out to identify and characterize equilibrium structures and transition structures on the 1-oxo-3-hydroxy-2-propene: Lewis acid potential energy surfaces, with the acids LiH, LiF, BeH2, and BeF2. Two equilibrium structures, one with the acid interacting with the C=O group and the other with the interaction occurring at the O–H group, exist on all surfaces. These structures are separated by transition structures that present the barriers to the interconversion of the two equilibrium structures. The structures with the acid interacting at the C=O group have the greater binding energies. Since the barriers to convert the structures with interaction occurring at the O–H group are small, only the isomers with interaction occurring at the C=O group could be experimentally observed, even at low temperatures. Charge-transfer energies were computed for equilibrium structures, and EOM-CCSD spin–spin coupling constants 2hJ(O–O), 1hJ(H–O), and 1J(O–H) were computed for equilibrium and transition structures. These coupling constants exhibit a second-order dependence on the corresponding distances, with very high correlation coefficients.

scholarly journals van der Waals potential energy surfaces from the exchange-hole dipole moment dispersion model

2016 ◽  
Vol 94 (12) ◽  
pp. 1049-1056 ◽  
Author(s):  
Joseph B. Dizon ◽  
Erin R. Johnson
Keyword(s):  
Dipole Moment ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Reference Data ◽  
Dispersion Model ◽  
Binding Energies ◽  
Coupled Cluster ◽  
Global Minima ◽  
Hybrid Functional ◽  
Energy Surfaces

The potential energy surfaces (PESs) of 28 simple van der Waals complexes, each consisting of a rare-gas (Rg) atom interacting with a linear molecule, are calculated using the exchange-hole dipole moment (XDM) dispersion model in conjunction with three base density functionals (HFPBE, PW86PBE, and a commensurate hybrid functional). Results are compared with literature coupled-cluster reference data. The quality of the computed PESs is assessed based on the positions of the global minima and the corresponding binding energies. Only the hybrid functional is found to provide generally reliable PESs. Dispersion-corrected HFPBE strongly underestimates the equilibrium intermolecular separations and predicts different global minima than the reference PESs for Rg–HCl, Rg–HBr, and two of the Rg–HCN complexes. Analysis of the binding-energy errors reveals that the performance of HFPBE degrades as the size of the Rg atoms increase down the group, while the performance of PW86PBE is significantly worse for strongly-polar molecules. PW86PBE, and to a lesser extent the hybrid, strongly overbind Kr–HF due to charge-transfer error. Despite this, the XDM-corrected hybrid functional displays the best overall error statistics and provides binding energies to within ca. 10 cm–1 of the coupled-cluster reference data at a greatly reduced computational cost.

scholarly journals Accuracy of Spin-Component Scaled ADC(2) Excitation Energies and Potential Energy Surfaces

2019 ◽  
Author(s):  
Attila Tajti ◽  
Levente Tulipan ◽  
Péter Szalay
Keyword(s):  
Potential Energy ◽  
Excited States ◽  
Canonical Form ◽  
Potential Energy Surfaces ◽  
Second Order ◽  
Spin Component ◽  
Excitation Energies ◽  
Order Algebraic ◽  
Energy Surfaces

In a recent paper of this Journal (Tajti and Szalay, JCTC 2019, 15, 5523) we have shown that failures of the CC2 method to describe Rydberg excited states, as well as potential energy surfaces of certain valence excited states can be cured by spin-component scaled (SCS) versions SCS-CC2 and SOS-CC2 by a large extent. In this paper, the related and popular Second Order Algebraic Diagrammatic Construction (ADC(2)) method and its SCS variants are inspected with the previously established methodology. The results reflect the similarity of the CC2 and ADC(2) models, showing identical problems in the case of the canonical form and the same improvement when spin-component-scaling is applied.

scholarly journals Unusual Complexes of P(CH)3 with FH, ClH, and ClF

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2846
Author(s):  
Janet E. Del Bene ◽  
Ibon Alkorta ◽  
José Elguero
Keyword(s):  
Potential Energy Surfaces ◽  
Symmetry Axis ◽  
Dipole Moments ◽  
Binding Energies ◽  
Coupling Constants ◽  
Coupled Cluster ◽  
Halogen Bonds ◽  
Energy Component ◽  
P Values ◽  
Energy Surfaces

Ab initio MP2/aug’-cc-pVTZ calculations have been performed to determine the structures and binding energies of complexes formed by phosphatetrahedrane, P(CH)3, and HF, HCl, and ClF. Four types of complexes exist on the potential energy surfaces. Isomers A form at the P atom near the end of a P-C bond, B at a C-C bond, C at the centroid of the C-C-C ring along the C3 symmetry axis, and D at the P atom along the C3 symmetry axis. Complexes A and B are stabilized by hydrogen bonds when FH and ClH are the acids, and by halogen bonds when ClF is the acid. In isomers C, the dipole moments of the two monomers are favorably aligned but in D the alignment is unfavorable. For each of the monomers, the binding energies of the complexes decrease in the order A > B > C > D. The most stabilizing Symmetry Adapted Perturbation Theory (SAPT) binding energy component for the A and B isomers is the electrostatic interaction, while the dispersion interaction is the most stabilizing term for C and D. The barriers to converting one isomer to another are significantly higher for the A isomers compared to B. Equation of motion coupled cluster singles and doubles (EOM-CCSD) intermolecular coupling constants J(X-C) are small for both B and C isomers. J(X-P) values are larger and positive in the A isomers, negative in the B isomers, and have their largest positive values in the D isomers. Intramolecular coupling constants 1J(P-C) experience little change upon complex formation, except in the halogen-bonded complex FCl:P(CH3) A.

scholarly journals Chemical verification of variational second-order density matrix based potential energy surfaces for the N2 isoelectronic series

2010 ◽  
Vol 132 (11) ◽  
pp. 114112 ◽  
Author(s):  
Helen van Aggelen ◽  
Brecht Verstichel ◽  
Patrick Bultinck ◽  
Dimitri Van Neck ◽  
Paul W. Ayers ◽  
...  
Keyword(s):  
Potential Energy ◽  
Density Matrix ◽  
Potential Energy Surfaces ◽  
Second Order ◽  
Isoelectronic Series ◽  
Energy Surfaces
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