Search

A new global many-body expansion potential energy surface for the ground electronic state of HO2 is constructed. All ab initio energy points are employed using aug-cc-pV(Q+d)Z and aug-cc-pV(5+d)Z basis sets at the multi-reference conformational interaction level and then extrapolated to the complete basis set limit. The topographic characteristics of the global potential energy surface for HO2 (X2A'') are discussed in detail and compared with experimental results, showing a good agreement. We subsequently consider the O(3P) + OH(2Π) → O2(3Σ- g) + H(2S) reaction using the time-dependent wave packet method and calculate dynamic behaviors, including the vibration–rotation distribution and reaction probabilities. The results indicate that the new potential energy surface is suitable for the dynamic investigations of O(3P) + OH(2Π) → O2(3Σ- g) + H(2S), and can be used as a component for potential energy surfaces to construct larger oxygen/hydrogen containing systems.

It has been established that the proton transfer dynamics of P + ( P 3 ) + H 2 ( X 1 Σ g + ) → P H + ( A 2 Δ ) + H ( S 2 ) play an important role in determining the chain reaction of phosphorus-containing P H n + ( n = 0 − 4 ) compounds in the planetary ionosphere. This work presents an accurate global potential energy surface (PES) of P H 2 + ( 2 1 A ′ ) for the first time by fitting extensive ab initio energies from the aug-cc-pV(T, Q)Z level of theory using the multi-reference configuration interaction method including Davidson correction, and extrapolating the points to the complete basis set limit. The spectral parameters of PH+(A 2Δ) and H 2 ( X 1 Σ g + ) are shown to be in agreement with the data available in previous literature. Meanwhile, a detailed study of the topographical features of the global PES could be used as a reliable photolytic kinetic theory for the P + ( P 3 ) + H 2 ( X 1 Σ g + ) reaction. Furthermore, to demonstrate the validity of the new PES, we have explicitly taken into account the P + ( P 3 ) + H 2 ( X 1 Σ g + ) ( v = 0 , j = 0 ) → P H + ( A 2 Δ ) + H ( S 2 ) reaction, and assessed its feasibility in terms of reaction dynamics by calculating the integral cross-section via the time-dependent wave packet and quasi-classical trajectory approaches. The consequent results indicate that the new PES is suitable for thermochemical reactions.

Electronic and vibrational spectroscopic studies of molecules are of crucial importance to characterizing a molecule and detecting the molecular species in different environments. In this review article, we summarized some important theoretical methods to calculate high-resolution electronic spectra and ro-vibrational states for small molecular systems with the inclusion of vibronic and ro-vibrational couplings, respectively. We have also reviewed a number of theoretical studies exploring some interesting organic chromophores like indole, isoalloxazine, transition metal trifluoride CoF3 and NiF3, and molecular ions like protonated rare gases and azido ions. These studies involve the calculation of spectroscopic features based on analytical potential energy surfaces (PESs) constructed using high-level ab initio energies. The topology of the PESs has been explored for these selected systems. The vibronic spectra and ro-vibrational states calculated using various theoretical methods and their comparison to available experimental results are reported in this review.

In this paper, we analyse the phase space structure of the roaming dynamics in a 2 degree of freedom potential energy surface consisting of two identical planar Morse potentials separated by a distance. This potential energy surface was previously studied in Carpenter B K et al (2018 Regul. Chaotic Dyn. 23 60–79), and it has two potential wells surrounded by an unbounded flat region containing no critical points. We study the phase space mechanism for the transference between the wells using the method of Lagrangian descriptors.

Polymorphs of MnO2 have been studied extensively for their potential application in rechargeable batteries which provide attractive structures as the host for the cation insertion. In this study, the simplest form of δ-MnO2 has been taken as the representative of layered MnO2 and the ion diffusion performance is carefully examined. The potential energy surfaces of Li+, Na+, K+, NH4 +, Mg2+, Zn2+, Ca2+ and Al3+ ion diffusing in the 1T-δ-MnO2 are firstly obtained within the density functional theory framework, which give a comprehensive and detailed view of the diffusing process. We not only assess the 1T-δ-MnO2 as candidate electrode material quantitatively but also elucidate the influence of the cooperative Jahn–Teller effect which governs multivalent diffusion in the intuitive and clear view. Our findings are well matched with the reported results and lead to practical and implementable guidelines to find MnO2-based fast-diffusion multivalent ion conductors.

A global potential energy surface (PES) of the ground state of SiH 2 + system is built by using neural network method based on 18223 ab initio points. The topographic properties of PES are presented and compared with previous theoretical and experimental studies. The results indicate that the spectroscopic parameters obtained from the new PES are in good agreement with the experimental data. In order to further verify the validity of the new PES, a test dynamics calculation of the Si+ + H2 (v 0 = 2, j 0 = 0) → H + SiH+ reaction has been carried out by using the time-dependent wave packet method. The integral cross sections and rate constants are computed for the title reaction. The reasonable dynamical behavior indicates that the newly constructed PES is suitable for relevant dynamics investigations.

Quasi-classical trajectory (QCT) calculations are reported for the H+LiH (v = 0–2, j = 0) → Li+H2 reaction on a new ground electronic state global potential energy surface (PES) of the LiH2 system. Reaction probability and integral cross sections (ICSs) are calculated for collision energies in the range of 0 eV–0.5 eV. Reasonable agreement is found in the comparison between present results and previous available theoretical results. We carried out statistical analyses with all the trajectories and found two main distinct reaction mechanisms in the collision process, in which the stripping mechanism (i.e., without roaming process) is dominated over the collision energy range. The polarization dependent differential cross sections (PDDCSs) indicate that forward scattering dominates the reaction due to the dominated mechanism. Furthermore, the reactant vibration leads to a reduction of the reactivity because of the barrierless and attractive features of PES and mass combination of the system.

Based on a new global potential energy surface of SiH 2 + ( X 2 A 1 ) , the exact quantum dynamical calculation for the H(2 S) + SiH+(X1Σ+) → H2 + Si+ reaction has been carried out by using the Chebyshev wave packet method. The initial state specified (ν i = 0, j i = 0) probabilities, integral cross sections (ICS) and thermal rate constants of the title reaction are calculated. All partial wave contributions up to J = 90 are calculated in exact quantum calculation including the full Coriolis coupling (CC) effect. The dynamical behaviors of probabilities, ICSs and rate constants are found to be in accord with an exothermic reaction without potential barrier. By comparing the probabilities of CC with the corresponding centrifugal sudden (CS) approximation ones, it can be concluded that neglecting CC effect will decrease the collision time, increase the amplitude of oscillation and lead to overestimation or underestimation of the reaction probability. For ICSs and rate constants, it is found that the deviation of CC and CS ICSs is small in the most of collision energy range except for the range of 0 eV–0.05 eV, while the deviation of both rate constants is considerable in the temperature range of 16 K–1000 K.

An angular momentum projected potential-energy-surface (PES) calculation, which takes both rotational symmetry restoration and multi-quasiparticle excitation into account, is developed by using the macroscopic-microscopic model and the projected shell model (PSM). Within this method, it may become possible to modify the excitation spectra which are influenced by shape-softness of nuclei, including high-K states. As our first example, this method is adopted to study the collective and multi-quasiparticle excitations of 178Hf, and the results are in good agreement with the existing experimental data. In addition, as for the dominant structure of non-collective 6+ bands, the conflict between experimental result and the previous PSM calculation is clarified.

The nuclear and Coulomb potentials between deformed nuclei with octupole deformations and arbitrary orientations are evaluated numerically. The effects of the octupole deformation on the potential between nuclei and the potential energy surface (PES) used in the description of the production of super-heavy nuclei (SHN) by heavy-ion fusion reactions are investigated in the di-nuclear system model. It is found that the nuclear octupole deformation significantly changes the shape of the PES, which may influence the fusion probability of the SHN. Also, PESs in the tip-belly and belly-belly cases are investigated. Finally, the quasi-fission barriers in the tip-tip and belly-belly cases are evaluated. It is found that the quasi-fission barriers of the belly-belly case are generally larger than those of the tip-tip case.

The potential energy surface of H(13) proton in base cytosine of the DNA molecules is calculated at the Gaussian 98 MP2/6-311G(d,p) level. Two potential wells are found. One corresponds to the normal cytosine, while the other corresponds to its trans-imino tautomer. The estimated tunneling probability of the H(13) proton from one well to another well shows that the life time of the proton staying in one of these wells is about 600 yrs. It is too long to let tautomers of cytosine be in thermodynamical equilibrium in a room temperature gas phase experiment.

A quasiclassical trajectory study with the sixth-order explicit symplectic algorithm for the N(4S)+O2(X3Σg−)→NO (X2Π)+O(3P) reaction has been reported by employing a new ground potential energy surface. We have discussed the influence of the relative translational energy, the vibrational and rotational levels of O2 molecules on the total reaction cross section. Thermal rate constants at temperatures 300, 600, and 1000 K determined in this work for the reaction are 4.4×107, 1.8×1010, and 3.1×1011 cm3mol−1s−1, respectively. It is found that they are in better agreement with the experimental data than previous theoretical values.

Starting from the content of the shell model space and using a simple symplectic as a weight Hamiltonian, the relative positions of different symplectic irreducible representations are deduced. Applying a geometrical mapping leads to a microscopically derived Potential-Energy-Surface. After smoothing this surface and fitting a mass parameter to the first excited 6+-state in the ground state band, the spectrum of a nucleus can be reproduced qualitatively. The method is also used to obtain a first estimation of the quadrupole Potential Energy Surface of any nucleus, allowing to obtain information about the structure of the nucleus in question. Of special interest is the prediction of the structure of nuclei away from the valley of stability and of super-heavy nuclei. The method will be illustrated at184W. One objective is to show that the Pauli Exclusion Principle is the main driving force for the structure of a nucleus, though some further microscopic input has to be used.

An interaction potential of the Ne?HCl van der Waals complex is obtained by utilizing the Huxley analytic potential function to fit the accurate interaction energy data, which have been computed at the coupled cluster singles and doubles including connected triple excitations level and with the augmented correlation consistent polarized valence quintuple zeta basis set extended with a set of 3s3p2d1f1g mid-bond functions [CCSD (T)/aug-cc-pV5Z-33211]. The close coupling calculation of state-to-state partial cross sections for collision of Ne with HCl is first performed by employing the fitted interaction potential. This calculation is performed at the incident energies: 40, 60, 75 and 100 meV, separately. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic state-to-state partial cross sections are discussed in detail. Two maxima are present in the rotationally inelastic partial cross sections and they originate from different mechanisms.

The vibration states of transition molecule S2O, including both bending and stretching vibrations, are studied in the framework of dynamical symmetry groups . We get all the vibration spectra of S2O by fitting 22 spectra data with 10 parameters. The fitting rms of the Hamiltonian is 2.12 cm-1. With the parameters and Lie algebraic theory, we give the analytical expression of the potential energy surface, which helps us to calculate the dissociation energy and force constants of S2O in the electronic ground state.

The strong shell effects of the magic nuclei 208Pb, 132Sn and 102Sn are the origin of valleys on the potential energy surfaces (PES) of the superheavy nucleus 294118 and of the alpha emitters 212Po and 106Te. We use the most advanced asymmetric two-centre shell model allowing us to obtain shell and pairing corrections which are added to the Yukawa plus exponential model deformation energy. For the first time the alpha valley of a nucleus (106Te) calculated by using the macroscopic–microscopic method is clearly seen on a PES. The α-decay half-lives calculated within fission theories (analytical superasymmetric fission model, universal curve, semiempirical formula based on fission theory) are very close to the experimental ones. The increased deviations in the neighbourhood of magic numbers of nucleons, present in other frequently used relationships (e.g. Viola–Seaborg formula), are smoothed out by the semiempirical formula based on fission theory.

Influence of the nuclear deformation on the potential energy surface (PES) in a di-nuclear system is studied in details. It is found that the PES shape changes greatly due to the deformation effect. The top point of the PES could be reduced significantly, which implies that the optimum excitation energy could also be reduced greatly and may enhance the formation probability of the compound nucleus. The dynamical deformation as a function of the reaction time in the reaction process is dramatic. The Z/N ratios of fragments tend to follow that of the compound nucleus during the nucleon exchange process, but to fluctuate.

An accurate potential energy surface for the Li + –H2 system has been calculated ab initio at an H–H distance of 1.449 a0, using an extended geminal model. The potential has been used to find elastic and inelastic total and transport cross sections, which have subsequently been used in moment-type transport calculations with a Kramers–Moyal-type expansion of the collision integral. The ion mobilities have also been measured at 295 K and E/n0 values from 10 to 450 Td, which corresponds to mean centre-of-mass energies from 0.04 to 7 eV. The agreement between experimental and calculated values is excellent below 220 Td. At higher E/n0 values, the agreement deteriorates gradually, possibly because of the neglect of vibrational excitation.

Validity of adiabatic assumption is discussed within the constrained Hartree-Fock theory for self-conjugate nucleus Kr-72. It is shown that the adiabatic assumption does not provide a correct description for the nature of nucleus when a, configuration change is involved. The excited Hartree-Fock states and the continuously-connected constrained Hartree-Fock states are given for the first time by applying the configuration dictated constrained Hartree-Fock theory with Gogny force. The importance of self-consistency between the mean-field and the single particle wave functions is emphasized even when a small number of nucleons are involved in the configuration change.

We have measured time-resolved optical absorption spectra following the excitation of the self-trapped excitons (STEs) in NaCl from the lowest triplet state to the next higher electron-excited state. In addition to the rapid reduction of the band due to the electron transition of the STE (STE band), a new absorption band peaked between the STE band and the F band is found to be temporarily generated. The heights of the new band and that of the STE band show anticorrelated oscillations with a period of 1 ps and moreover the new band disappears and the STE band recovers within 7 ps after the excitation. It is shown that the new band is due to the transition from the adiabatic potential energy surface on which the lowest STE is located and the oscillation is interpreted to be a motion of a wave packet on the adiabatic potential energy surface. We find also that the F band grows in the relaxation process.

A globally accurate potential energy surface is reported for the electronic ground-state H2O+. The ab initio energies utilized to map the potential energy surface are calculated at the multireference configuration interaction method employing the aug-cc-pVQZ basis set and the full valence complete active space wave function as reference. In order to improve accuracy of the resulting raw ab initio energies, they are then extrapolated to the complete basis set limit and most importantly to the full configuration-interaction limit by semiempirically correcting the dynamical correlation using the double many-body expansion-scaled external correlation method. The topographical features of the current potential energy surface were examined in detail, which agree nicely with those of other theoretical work.

A new potential energy surface (PES) for the first excited singlet state of ClNO was calculated with the coupled electron pair approximation (CEPA) method. This PES could be used without any empirical corrections in subsequent three-dimensional dynamical calculations with a L2 amplitude density method of time-independent scattering theory. Absolute photodissociation rates for producing the NO fragment, in particular rotational-vibrational states were calculated for the lowest seven initial vibrational states, of ClNO. A shift of the D and C band peaks to shorter wavelengths with increasing temperature is predicted.

Adiabatic potential energy surfaces (APESS) of the FH(CN-) centre in KCl and CsCl are calculated for the excited and ground states. It is shown that in CsCl the APES of the excited state intersects that of the ground state on the path of de-excitation leading to the quenching of emission. In KCl, the opposite situation is obtained in agreement with experiment. The calculation for CsCl shows a rapid variation of the dipole moment of the CN- molecule near the crossing region. The electronic-to-vibrational energy transfer (EV transfer) between the F centre and CN- molecule is discussed in terms of the non-radiative transitions between the two intersecting APESS. The dipole-dipole coupling between the F centre and CN- molecule (Dexter-Farster theory) is also considered to analyse certain aspects of the EV transfer.

The product rotational polarizations of reaction Li+HF→LiF+H at different collision energies, as well as at the different vibrational states and rotational states, are calculated by using the quasi-classical trajectory method based on a new potential energy surface constructed by Aguado et al. [J. Chem. Phys. 119 (2003) 10088]. We investigate the alignment and the orientation of the product molecule by calculating the P(θr, r) distributions describing polar angle distribution, the P(θr) distributions describing the k–j' correlation and the P(r) distributions describing the k–k'–j' correlation. We also explore the dependence of reaction probabilities and cross sections on the rotational and vibrational quantum number of the title reaction. It is concluded that the vibrational state has more important impact on the angular distribution, reaction probability and cross section.