Potential energy surface

About: Potential energy surface is a research topic. Over the lifetime, 11674 publications have been published within this topic receiving 307691 citations.

Sub-microhartree accuracy potential energy surface for H3+ including adiabatic and relativistic effects. I. Calculation of the potential points

Abstract: Sixty-nine points of the Born–Oppenheimer (BO) potential energy surface (PES) for the ground state of H3+ have been computed using explicitly correlated Gaussian wave functions with optimized nonlinear parameters. The calculated points have an absolute error of about 0.02 cm−1 (0.1 microhartree), i.e., they are by at least one order of magnitude more accurate than ever reported. Similarly accurate adiabatic and relativistic corrections have also been evaluated by means of the Born–Handy formula and by direct perturbation theory (DPT), respectively.

Theoretical study of the internal charge transfer in aminobenzonitriles

Abstract: The lower excited states for the molecules aminobenzonitrile (ABN) and (dimethylamino)benzonitrile (DMABN) have been studied as a function of the twisting and wagging motion of the amino group. Theoretical calculations have been performed using the complete active space (GAS) SCF method in combination with multiconfigurational second Order perturbation theory (CASPT2): Basis sets of the ANO-type (C,N/3s2p1d and H/2s) were employed. Ground state geometries were optimized at the CASSCF level. The excitation energies were computed as function of a twist angle, where the amino group is rotated with respect to the benzonitrile plane, and for two values of the wagging angle (0 and 21 degrees). The influence of the wagging angle in the nontwisted molecules was also analyzed. The results fully confirm the twist intramolecular charge transfer (TICT) model proposed to explain the dual fluorescence phenomena occurring in DMABN. The absence of the low frequency part of the fluorescence spectrum in ABN in explained by the shape of the potential energy surface along the isomerization path, due to the large energy gaps among the interacting states, which prevents the amino group from rotating into the TICT state. Calculated transition energies (absorption and emission), structural, and electrical properties of the ground and excited states are in agreement with available experimental information.

Global ab initio ground-state potential energy surface of N4.

Abstract: We present a global ground-state potential energy surface for N4 suitable for treating high-energy vibrational-rotational energy transfer and collision-induced dissociation in N2–N2 collisions. To obtain the surface, complete active space second-order perturbation theory calculations were performed for the ground singlet state with an active space of 12 electrons in 12 orbitals and the maug-cc-pVTZ triple zeta basis set. About 17 000 ab initio data points have been calculated for the N4 system, distributed along nine series of N2 + N2 geometries and three series of N3 + N geometries. The six-dimensional ground-state potential energy surface is fitted using least-squares fits to the many-body component of the electronic energies based on permutationally invariant polynomials in bond order variables.

Substituent effects on the edge-to-face aromatic interactions.

Abstract: The edge-to-face interactions for either axially or facially substituted benzenes are investigated by using ab initio calculations. The predicted maximum energy difference between substituted and unsubstituted systems is ∼0.7 kcal/mol (∼1.2 kcal/mol if substituents are on both axially and facially substituted positions). In the case of axially substituted aromatic systems, the electron density at the para position is an important stabilizing factor, and thus the stabilization/destabilization by substitution is highly correlated to the electrostatic energy. This results in its subsequent correlation with the polarization and charge transfer. Thus, the stabilization/destabilization by substitution is represented by the sum of electrostatic energy and induction energy. On the other hand, the facially substituted aromatic system depends on not only the electron-donating ability responsible for the electrostatic energy but also the dispersion interaction and exchange repulsion. Although the dispersion energy i...

Melting and freezing of small argon clusters

Abstract: An investigation of melting, freezing, and coexistence phenomena is presented for small clusters using Ar7, Ar8, Ar13, and Ar14 as specific representative examples. Combining the results of molecular dynamics simulations, especially short‐time kinetic energy averages and quenching, with accurate calculations of the local minima and transition states illuminates the relationship between the potential energy surface and dynamical processes. The results are consistent with a recent general defect theory of melting.