Ab initio calculations of accurate dissociation energy and analytic potential energy function for the second excited state B^1∏ of ^7LiH

The reasonable dissociation limit of the second excited singlet state B1∏ of ^7LiH molecule is obtained. The accurate dissociation energy and equilibrium geometry of the B^∏ state are calculated using a symmetry-adaptedcluster configuration interaction method in full active space. The whole potential energy curve for the B1H state is obtained over the internuclear distance ranging from about 0.10 nm to 0,54 nm, and has a least-square fit to the analytic Murrell-Sorbie function form. The vertical excitation energy is calculated from the ground state to the B^1∏ state and compared with previous theoretical results. The equilibrium internuclear distance obtained by geometry optimization is found to be quite different from that obtained by single-point energy scanning under the same calculation condition. Based on the analytic potential energy function, the harmonic frequency value of the B^1∏ state is estimated. A comparison of the theoretical calculations of dissociation energies, equilibrium interatomic distances and the analytic potential energy function with those obtained by previous theoretical results clearly shows that the present work is more comprehensive and in better agreement with experiments than previous theories, thus it is an improvement on previous theories.

Ab initio calculation of accurate dissociation energy, potential energy curve and dipole moment function for the A^1∑＋ state ^7LiH molecule

The reasonable dissociation limit of the A^1∑＋ state ^7LiH molecule is obtained. The accurate dissociation energy and the equilibrium geometry of this state are calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space for the first time, The whole potential energy curve and the dipole moment function for the A^1∑＋ state are calculated over a wide internuclear separation range from about 0.1 to 1.4 nm. The calculated equilibrium geometry and dissociation energy of this potential energy curve are of Re=0.2487 nm and De=1.064eV, respectively. The unusual negative values of the anharmonicity constant and the vibration-rotational coupling constant are of ωeXe=-4.7158cm^-1 and αe=0.08649cm^-1, respectively. The vertical excitation energy from the ground to the A^1∑＋ state is calculated and the value is of 3.613eV at 0.15875nm （the equilibrium position of the ground state）. The highly anomalous shape of this potential energy curve, which is exceptionally flat over a wide radial range around the equilibrium position, is discussed in detail. The harmonic frequency value of 502.47cm^-1 about this state is approximately estimated. Careful comparison of the theoretical determinations with those obtained by previous theories about the A^1∑＋ state dissociation energy clearly shows that the present calculations are much closer to the experiments than previous theories, thus represents an improvement.

Accurate double many-body expansion potential energy surface of HS_2(A^2A') by scaling the external correlation

A globally accurate single-sheeted double many-body expansion potential energy surface is reported for the first excited state of HS_2 by fitting the accurate ab initio energies, which are calculated at the multireference configuration interaction level with the aug-cc-pVQZ basis set. By using the double many-body expansion-scaled external correlation method,such calculated ab initio energies are then slightly corrected by scaling their dynamical correlation. A grid of 2767 ab initio energies is used in the least-square fitting procedure with the total root-mean square deviation being 1.406 kcal · mol^（-1）.The topographical features of the HS_2（A_2A＇） global potential energy surface are examined in detail. The attributes of the stationary points are presented and compared with the corresponding ab initio results as well as experimental and other theoretical data, showing good agreement. The resulting potential energy surface of HS_2（A_2A＇） can be used as a building block for constructing the global potential energy surfaces of larger S/H molecular systems and recommended for dynamic studies on the title molecular system.

Theoretical Study with Rovibrational and Dipole Moment Calculation of the SiO Molecule

Via CASSCF/MRCI and RSPT2 calculations (single and double excitation with Davidson correction) the potential en- ergy curves of 20 electronic states in the representation 2S+1Λ(±)of the molecule SiO have been calculated. By fitting these potential energy curves to a polynomial around the equilibrium internuclear distance re, the harmonic frequency ωe, the rotational constant Be, and the electronic energy with respect to the ground state Te have been calculated. For the considered electronic states the permanent dipole moment μ have been plotted versus the internuclear distance r. Based on the canonical functions approach, the eigenvalues Ev, the rotational constant Bv and the abscissas of the turning points rmin and rmax have been calculated. The comparison of these values to the experimental and theoretical results available in the literature is presented. In the present work 8 higher electronic states have been studied theoretically for the first time.

Theoretical Calculation of the Low-Lying Electronic States of the Molecule PbO

The potential energy curves of the lowest 20 electronic states in the representation 2s+1Λ(±) of the molecule PbO have been investigated via ab initio CASSCF and MRCI (single and double excitations with Davidson correction) calculations. The spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te with respect to the ground state have been calculated along with the permanent dipole moment for the different bound investigated electronic states. By using the canonical functions approach, the eigenvalues Ev, the rotational constant Bv and the abscissas of the turning points Rmin and Rmax have been calculated. The comparison of these values with those available in the literature shows a very good agreement.

Theoretical Calculation of the Low-Lying Electronic States of the Molecule BaS

Complete Active Space Self Consistent Field (CASSCF) with Multireference Configuration Interaction (MRCI) and Rayleigh-Schrodinger Perturbation Theory (RSPT2-RS2) methods have been used to investigate the potential energy curves for the 12 low-lying singlet and triplet electronic states in the representation 2s+1Λ(+/-) of the molecule BaS with Davidson corrections. The harmonic frequency we, the internuclear distance Re, the electronic energy with respect to the ground state Te, the rotational constants Be and the permanent dipole moment have been calculated for these electronic states. The eigenvalues Ev, the rotational constants Bv, the centrifugal distortion constant Dv and the abscissas of the turning points Rmin and Rmax have been investigated using the canonical functions approach. Nine new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement.

<i>Ab-Initio</i>Calculations of 27 Electronic States of the BP⁺Ion-Molecule

The theoretical investigation of the potential energy curves, in the representation 2s+1Λ(+/-), of the 27 low-lying Doublet and Quartet electronic states of the BP+ molecular ion has been performed with the methods in quantum chemistry, the Complete Active Space Self Consistent Field (CASSCF) and the Multireference Configuration Interaction (MRCI) calculations. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have also been calculated. Twenty-three new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. These investigated data can be a conducive to further work on BP+ molecular ion in both experimental and theoretical research.

Theoretical Calculation of the Low-Lying Electronic States of the Molecule ScSe

Theoretical investigation of the lowest electronic states of ScSe molecule, in the representation 2s+1Λ(+/-), has been performed via CASSCF and MRCI + Q (single and double excitations with Davidson correction) calculations. The calculated potential energy curves (PECs), permanent dipole moment curves (PDMCs), and spectroscopic constants are reported for the 14 lowest electronic states. The comparison of the present results with the rare available theoretical data in literature shows an overall good agreement. To the best of our knowledge, 13 electronic states of the ScSe molecule are not yet investigated either experimentally or theoretically;they are investigated in the present work for the first time.

Ab Initio Calculation of the Electronic States of ScTe Molecule below 19,500 cm-1

The potential energy curves (PECs) of the16 lowest electronic states in the representation 2s+1Λ (+/-) of the molecule ScTe have been investigated via ab initio CASSCF and MRCI (single and double excitations with Davidson correction) calculations. The permanent dipole moment curves (PDMCs) and the spectroscopic constants such as vibrational harmonic frequency ωe, the internuclear distance at equilibrium Re, the rotational constant Be, and the electronic transition energy Te with respect to the ground state have been calculated for the different bound investigated electronic states. The comparison of the present results with the rare available theoretical data in literature shows an overall good agreement. To the best of our knowledge, 15 electronic states of the ScTe molecule are not yet investigated either experimentally or theoretically, they are investigated in the present work for the first time.

Ab initio calculations on accurate dissociation energy, equilibrium geometry, and analytic potential energy function for the 6~3Π state of ~7LiH molecule

The accurate dissociation energy and equilibrium geometry of the ball state of ^7LiH molecule is calculated using a symmetry-adapted-cluster configuration-interaction method in full active space. And the calculated results are 0.2580 eV and 0.1958 nm for the dissociation energy and equilibrium geometry, respectively. The whole potential energy curve for the b^3∏ state is also calculated over the internuclear separation range from about 0.10 to 0.54 nm. The results are fitted by the Murrell-Sorbie function. It is found that the Murrell-Sorbie function form, which is mainly used to fit the ground-state potential energy function, is well suitable for the excited triplet b^3∏ state. The vertical excitation energy from the ground state to the b^3∏ state is calculated to be 4.233 eV. Based on the analytic potential energy function, the harmonic frequency of 610.88 cm^-1 about this state is firstly estimated. Compared with other theoretical results, this work is the most complete effort to deal with the analytic potential energy function and the harmonic frequency of this state.

Thermodynamic Equilibrium of the Saturated Fluid with a Free Surface Area and the Internal Energy as a Function of the Phase-Specific Volumes and Vapor Pressure

This study is concerned with describing the thermodynamic equilibrium of the saturated fluid with and without a free surface area A. Discussion of the role of A as system variable of the interface phase and an estimate of the ratio of the respective free energies of systems with and without A show that the system variables given by Gibbs suffice to describe the volumetric properties of the fluid. The well-known Gibbsian expressions for the internal energies of the two-phase fluid, namely for the vapor and for the condensate (liquid or solid), only differ with respect to the phase-specific volumes and . The saturation temperature T, vapor presssure p, and chemical potential are intensive parameters, each of which has the same value everywhere within the fluid, and hence are phase-independent quantities. If one succeeds in representing as a function of and , then the internal energies can also be described by expressions that only differ from one another with respect to their dependence on and . Here it is shown that can be uniquely expressed by the volume function . Therefore, the internal energies can be represented explicitly as functions of the vapor pressure and volumes of the saturated vapor and condensate and are absolutely determined. The hitherto existing problem of applied thermodynamics, calculating the internal energy from the measurable quantities T, p, , and , is thus solved. The same method applies to the calculation of the entropy, chemical potential, and heat capacity.

Low-lying electronic states of CuN calculated by MRCI method

The high accuracy ab initio calculation method of multi-reference configuration interaction（MRCI） is used to compute the low-lying eight electronic states of CuN.The potential energy curves（PECs） of the X;∑;,1;Π,2;∑;,1;△,1;△,1;∑;,1;Π,and;∑;in a range of R=0.1 nm-0.5 nm are obtained and they are goodly asymptotes to the Cu（;S;） + N（;S;） and Cu（;S;）+N（;D;） dissociation limits.All the possible vibrational levels,rotational constants,and spectral constants for the six bound states of X;∑;,1;Π,2;∑;,1;△,1;∑;,and 1;Π are obtained by solving the radial Schrdinger equation of nuclear motion with the Le Roy provided Level 8.0 program.Also the transition dipole moments from the ground state X;∑;to the excited states 1;Π and 2;∑;are calculated and the result indicates that the 2;∑-X;∑ transition has a much higher transition dipole moment than the 1;Π-X;∑;transition even though the l;Π state is much lower in energy than the 2;∑;state.

Programmable repulsive potential for tight-binding from Chen-Möbius inversion theorem

An accurate total energy calculation is essential in materials computation.To date,many tight-binding(TB)approaches based on parameterized hopping can produce electronic structures comparable to those obtained using first-principles calculations.However,TB approaches still have limited applicability for determining material properties derived from the total energy.That is,the predictive power of the TB total energy is impaired by an inaccurate evaluation of the repulsive energy.The complexity associated with the parametrization of TB repulsive potentials is the weak link in this evaluation.In this study,we propose a new method for obtaining the pairwise TB repulsive potential for crystalline materials by employing the Chen-Möbius inversion theorem.We show that the TB-based phonon dispersions,calculated using the resulting repulsive potential,compare well with those obtained by first-principles calculations for various systems,including covalent and ionic bulk materials and twodimensional materials.The present approach only requires the first-principles total energy and TB electronic band energy as input and does not involve any parameters.This striking feature enables us to generate repulsive potentials programmatically.

Six-dimensional potential energy surface of the dissociative chemisorption of HCl on Au(111) using neural networks

We constructed a six-dimensional potential energy surface(PES)for the dissociative chemisorption of HCl on Au(111)using the neural networks method based on roughly 70000 energies obtained from extensive density functional theory(DFT)calculations.The resulting PES is accurate and smooth,based on the small fitting errors and good agreement between the fitted PES and the direct DFT calculations.Time-dependent wave packet calculations show that the potential energy surface is very well converged with respect to the number of DFT data points,as well as to the fitting process.The dissociation probabilities of HCl initially in the ground rovibrational state from six-dimensional quantum dynamical calculations are quite diferent from the four-dimensional fixed-site calculations,indicating it is essential to perform full-dimensional quantum dynamical studies for the title molecule-surface interaction system.

Deconstructing Vibrational Motions on the Potential Energy Surfaces of Hydrogen-Bonded Complexes

Internal vibrations underlie transient structure formation,spectroscopy,and dynamics.However,at least two challenges exist when aiming to elucidate the contributions of vibrational motions on the potential energy surfaces.One is the acquisition of well-resolved experimental infrared spectra,and the other is the development of efficient theoretical methodologies that reliably predict band positions,relative intensities,and substructures.Here,we report size-specific infrared spectra of ammonia clusters to address these two challenges.Unprecedented agreement between experiment and state-of-the-art quantum simulations reveals that the vibrational spectra are mainly contributed by proton-donor ammonia.A striking Fermi resonance observed at approximately 3210 and 3250 cm^(−1)originates from the coupling of NH symmetric stretch fundamentals with overtones of free and hydrogen-bonded NH bending,respectively.These novel,intriguing findings contribute to a better understanding of vibrational motions in a large variety of hydrogen-bonded complexes with orders of magnitude improvements in spectral resolution,efficiency,and specificity.

An accurate three-dimensional potential energy surface for the He-Na_2 complex

An accurate three-dimensional potential energy surface(PES) for the He-Na2 van der Waals comple was calculated at the coupled cluster singles-and-doubles with noniterative inclusion of connecte triple(CCSD(T)) level of theory.A mixed basis set,aug-cc-pVQZ for the He atom and cc-pCVQZ for th sodium atom,and an additional(3s3p2d1f) set of midbond functions were used.The computed inte action energies in 819 configurations were fitted to a 96-parameter analytic potential model by leas squares fitting.The PES has two shallow wells corresponding to the T-shaped structure and the linea configuration,which are located at 12.5a0 and 14 a0 with depths of 1.769 and 1.684 cm-1,respectivel The whole potential energy surface exhibits weak anisotropy.Based on the fitted PES,state-to-stat differential cross sections were calculated.

锂电池基础科学问题(Ⅰ)——化学储能电池理论能量密度的估算

本文主要讨论电池的能量密度。基于热力学数据,根据能斯特方程,可以计算不同电化学反应体系的理论能量储存密度,从而了解化学储能体系理论能量密度的上限,了解哪些体系能够实现更高的能量密度,哪些材料具有更高的电压。

水泥土重力式围护结构水平变形简化计算方法

根据上海地区具体工程实例,通过归一化得到了水泥土重力式围护结构墙体的水平位移函数表达式,然后采用最小势能原理,推导了上海地区水泥土重力式围护结构墙体水平位移的简化计算公式,并对影响墙体位移的若干因素进行了分析.采用该墙体位移简化公式对上海地区十个工程进行了计算,结果表明计算值与实测值之间的平均相对误差为13.5%,从而验证了该方法的适用性.

波形钢腹板-混凝土组合箱梁截面变形的拟平截面假定及其应用研究

为使波形钢腹板-混凝土组合箱梁的正截面弯曲应力计算能够应用平截面假定,根据该组合箱梁模型试验在弹性阶段的应变实测数据和空间有限元计算结果,忽略波形钢腹板的抗弯贡献,假设上、下翼板的混凝土纵向正应变在弹性阶段符合“拟平截面假定”,并运用变分法理论进行了证明。算例表明据“拟平截面假定”计算的翼板应力计算值与有限元法计算结果吻合。“拟平截面假定”为波形钢腹板-混凝土组合箱梁的弯曲应力计算及抗弯承载力计算在理论上提供了必要的变形协调条件。

一种三杆并联机床的静力分析

推导了在重力和切削力作用下并联机床驱动力的计算方程 ,并对一种三杆并联机床进行了仿真计算。结果表明 ,该种并联机床进行切削加工时 ,各杆输出的驱动力比较均匀 ,没有突变 ,各杆驱动力最大不超过切削力的 1 .4倍 ;机床自重产生的驱动力在工作空间中无突变 ,并且在工作空间边缘处较大 ;为了克服机床自重 ,需要各杆输出较大的驱动力 。