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Publications (52)
How to find the boundary between microscopic and macroscopic worlds is always of great interest. Studies indicate that such a boundary may be in existence but has never been found so far. Here we find that there exists the smallest thickness of bulk layer at nano scale for pure heptane and hexadecane liquids. The characteristic nano thickness (CNT)...
In this paper, a light-induced Rh(III)-azobenzene (azo) complex in its two conformations (cis- and trans-form) is analyzed via density functional theory methods, focusing on the geometrical and electronic structure, linear and second-order nonlinear optical (NLO) properties, as well as UV-vis absorption spectra. The results show that trans-Rh exhib...
Block effective Hamiltonian theory (BEHT) is presented in this work. Configuration interaction functions are divided into P, Q, and R spaces. Effective Hamiltonian is constructed with the partitioning technique within the P space. The eigenvalue problem of the effective Hamiltonian is then solved iteratively. It is demonstrated that the ground-stat...
Polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment as toxic pollutants. In this study, quantum chemistry methods are used to study reactions of PAHs in both particle and gas phases. Seven theoretical methods are exploited to predict the reactive sites of 15 PAHs in the particle phase. Among these methods, the performance...
In this paper, eight complexes M-1, M-2, M-3 and M-4 (M = Ir or Rh) in the general formula [M(C^N)2(N^N)] (C^N = cyclometalated ligands and N^N = ancillary ligands) are systematically investigated by density functional theory (DFT) and time-dependent DFT methods. With the aim to study the influence of metal centers for nonlinear optical (NLO) respo...
Iterative multireference configuration interaction (IMRCI) has been exploited to calculate the properties of small molecules. Atomisation energies of CH2(¹A1), H2O, HF, CH(X²Π), OH(X²Π) and CH2(³B1), and singlet–triplet separations of CH2, NH2⁺, SiH2, and PH2⁺ are computed with MRCI and IMRCI. The accuracy of IMRCI is comparable to that of coupled-...
A new equation related to the surface tension and concentration of solute in the surface region is derived and a three-step procedure is proposed to determine the molecular area of surfactants in aqueous solution at saturation of the air–liquid surface. Based on their surface tension data, the molecular areas of hexyl, octyl and decyl trimethylammo...
Iterative multireference configuration interaction (IMRCI) is proposed. It is exploited to compute the electronic energies of H2O and CH2 (singlet and triplet states) at equilibrium and non-equilibrium geometries. The potential energy curves of H2O, CH2 (singlet and triplet states) and N2 have also been calculated with IMRCI as well as the Møller P...
Divergences of the single reference perturbation theories due to the addition of diffusion basis functions have been investigated for both closed-shell and open-shell molecular systems. It is found that the oscillatory range of perturbation energies of open-shell systems increases as the spin multiplicity of systems changes from 2 to 4. Feenberg tr...
Based on the complete active space multireference wavefunction, multireference Rayleigh–Schrödinger perturbation theory (MRSPT) is derived with the assumption that the orbital energies of active orbitals are the same as ε¯, an unknown parameter. In this work, ε¯ is optimized at the MRSPT2 level. The second and third order perturbation theories are...
Applications of the multireference linearized coupled-cluster single-doubles (MRLCCSD) to atomic and molecular systems have been carried out. MRLCCSD is exploited to calculate the ground-state energies of HF, H2O, NH3, CH4, N2, BF, and C2 with basis sets, cc-pVDZ, cc-pVTZ and cc-pVQZ. The equilibrium bond lengths and vibration frequencies of HF, HC...
Surface tension is one of the most important properties of liquid. A new theory is proposed and applied to the phenomena related to the surface tension of pure liquid compounds and strong electrolyte solutions. We first found that the phase transitions of pure liquid compounds from bulk to surface are exothermic and transition heats of 38 liquid co...
Configuration interaction calculation in complete active space is related to the numbers of active electrons and orbitals. However, configuration interaction energy is not a monotonically decreasing function of these two variables. Thus, the numbers of active electrons and orbitals are not proper variables to extrapolate the configuration interacti...
Natural population analysis (NPA) charge, Hirshfeld charge, electrostatic potential, average local ionization energy, orbital composition of lowest unoccupied molecular orbital (LUMO), condensed Fukui function and condensed dual descriptor were exploited to predict the reaction active sites of nucleophilic and electrophilic reactions of aromatic co...
The relationship between the bond angle and bond dipole moment is investigated. The atomic dipole moment corrected Hirshfeld (ADCH) charges are used to calculate the bond dipole moment. The electron localization function and its values at the bond critical points are exploited to analyze the bond’s electronic structures. Through analyzing the data...
Geometries of complexes HXeBr…C6H5X (X=H, CH3, NH2, N(CH3)2, NHCH3, OH, OCH3, CN, F, Cl, Br, I, COOH, SO3H, CF3) and its monomers are optimized with MP2/aug-cc-pVDZ (aug-cc-pVDZ-PP for Xe and I). The aug-cc-pVDZ-PP is a small core pseudopotential basis set. It ignores 28 electrons for Xe and I atoms. Two types of weak interactions, π…H bond and bif...
Electron affinities of F, Cl, OH, SH, CN, CH2, and NH2 have been computed with the second order multireference perturbation theory. The effects of basis set and size of the complete active space on accuracy of electron affinity have also been investigated. The results are compared with calculations performed with CASSCF, CASPT2, CCSD, CCSD(T), B3LY...
Predicting the reactivity of nucleophilic reaction at different sites has important theoretical and practical significance. Many prediction methods solely based on the electronic structure of reactants have been proposed. In this paper, detailed comparative analyses on the reliability of 14 methods are carried out and three series of molecules, car...
Surface adsorption of a solution is still a challenging problem in the thermodynamics of surfaces. In this work, a new thermodynamic state function is defined. The equilibrium condition of surface adsorption is that the differential of this state function is equal to zero. Based on this condition, we derived a new equation to describe surface adsor...
Predicting the reactivity of electrophilic substitution at different sites is of theoretical and practical significance, and many prediction methods based on the electronic structure of reactants have been proposed. We compared the reliability of 14 prediction methods, using 14 monosubstituted and 8 disubstituted benzenes as test sets. Methods refl...
A new multireference perturbation series is derived based on the Rayleigh-Schrödinger perturbation theory. It is orbitally invariant. Its computational cost is comparable to the single reference Møller-Plesset perturbation theory. It is demonstrated numerically that the present multireference second- and third-order energies are size extensive by t...
Understanding the nature of noncovalent interactions between nonpolar small molecules is not only theoretically interesting but also important for practical purposes. The interaction mechanism of three prototype dimers (H2)2, (N2)2, and (H2)(N2) are investigated by state-of-the-art quantum chemistry calculations and energy decomposition analysis. I...
The geometries of the ground and excited states of titanium dioxide, 1A 1, 1B 2, 3B 2, 1B 1, 3B 1, 1A 2 and 3A 2, have been optimized using Møller-Plesset second-order perturbation theory, density functional theory B3LYP, and time-dependent density functional theory TD-B3LYP methods. 1A 1, 1B 2, 3B 2, 1B 1 and 3B 1 have bent structures, while 1A 2...
Bond order is an important concept for understanding the nature of chemical bond. In this work, we propose a novel definition of bond order, called Laplacian bond order (LBO), which is defined as a scaled integral of negative parts of Laplacian of electron density in fuzzy overlap space. Many remarkable features of LBO are exemplified by numerous s...
Multiwfn is a multifunctional program for wavefunction analysis. Its main functions are: (1) Calculating and visualizing real space function, such as electrostatic potential and electron localization function at point, in a line, in a plane or in a spatial scope. (2) Population analysis. (3) Bond order analysis. (4) Orbital composition analysis. (5...
Charge preservation is a necessary condition in population analysis. However, one such constraint is not enough to solve the arbitrariness involved in the population analysis such as Hirshfeld population. This arbitrariness results in too small Hirshfeld charges and poor reproducibility of molecular dipolar moments. In this article, the preservatio...
Atomic charge is one of the simplest and the most intuitive description of charge distribution in chemical systems. It has great significance in theory and in practical applications. In this article we introduce the basic principles and special characteristics of twelve important computational methods for the determination of atomic charges and com...
The electron localization function (ELF) is an important tool to study electronic structure. In this article, the concept of electron localization is introduced and the overlap between the physical meaning and functional form of the ELF is discussed in detail from two points of view: electron pair density and kinetic energy density. Additionally, w...
The concept of the molecular orbital composition is often involved in quantum chemistry literatures. However, no enough emphasis has been placed on the corresponding calculation methods, and even there exist some serious misunderstandings. In this article, the basic concepts and calculation methods of composition of basis functions, atomic orbitals...
A few open-shell molecules are taken as examples in order to examine the performance of the open-shell perturbation theory for electron correlation (J Chem Theory Comput, 2009, 5: 931–936). The convergence of the perturbation series is shown to be stable for the doublet state of NH2 at both the equilibrium and stretched geometries. The equilibrium...
The parallelism and convergence of the approximate and analytical integration methods on solvation effect calculation were investigated by simulating the solute cavity with polyhedrons. We find that these two methods have excellent parallelismfor the 40 neutral molecules studied. The parallelismis poor for the 27 anions and 20 cations studied as th...
The Davidson's method originally developed for eigenvalue problems was extended to solve large-scale linear equations. It can be used for symmetrical and nonsymmetrical matrices. Numerical results presented in this study demonstrate that the present scheme is much more effective than conjugate gradient method and biconjugate gradient method for sym...
A new single reference perturbation partition is proposed for restricted open-shell Hartree−Fock (ROHF) and complete active space self-consistent field (CASSCF) orbitals. It is a sum of one-particle operator which is implicitly defined. When the operator acts on a ROHF or CASSCF orbital, the resultant eigenvalue is the orbital’s corresponding orbit...
We extended the Davidson method, which was used to solve the standard eigenvalue problem, to solve the generalized eigenvalue problem and proposed the corresponding block iterative algorithm. Through theoretical analysis and numerical calculation, we found that the block iterative algorithm was doomed to converge after finite iterations if the proc...
The size consistency of the multireference perturbation theory and multireference singly-excited and doubly-excited configuration interaction (MRSDCI) was investigated numerically with three super-molecular models composed of H2, He, and LiH monomers separated by a large distance. A small full configuration interaction was performed first over the...
The size consistency of the second and third order energies of the multireference perturbation theory (Chen F, Davidson E,
Iwata S. Int J Quant Chem, 2002, 86: 256) is investigated theoretically with a super-molecular model composed of N-hydrogen molecules separated by a large distance. It is found that the two perturbation series corresponding to...
The effectiveness of the approach for systematical reconstruction of higher order reduced density matrices with lower order ones, which was developed by Chen (Science in China B, 2006, 49: 402), was compared theoretically with that of Mazziotti's method through Harris model, by omitting the cumulant terms 3ΔM, 4ΔM in the latter method and the norma...
The size-consistency of the single reference perturbation series corresponding to two Hamiltonian partitions has been studied theoretically using an N hydrogen molecular model. One perturbation series corresponding to the so-called Epstein-Nesbet partition was found to be size consistent up to the fourth order, and another perturbation series (Chen...
We first obtained a closed form of the Wick’s theorem expressed in Grassman wedge product, which is similar to a binomial
expansion. With this new expansion, new reconstruction schemes for reduced density matrices are derived rigorously. The higher
order reduced density matrices are systematically decomposed into a sum of the lower order reduced de...
Photoabsorption cross-sections of water dimer and trimer anions are calculated with an ab initio molecular orbital method. Because the electron detachment energy of these small water cluster anions is less than 0.3 eV, all of the photoabsorption spectra in the near-infrared and visible region are due to the bound-free transitions. The theoretical s...
In this Letter, a case is reported where a small basis set superposition error (BSSE) dependence on the geometry leads to a large change in the optimized structure. The rotational potential energy curves of the p-difluorobenzene–N2 (p-DFB–N2) complex were calculated with MP2, MP3, MP4(SDQ) and basis sets at different levels. For all calculations wi...
Electronic spectra of ammoniated ammonium radicals, NH4(NH3)n, produced through the photolysis of ammonia clusters, are investigated with a laser photodepletion spectroscopy. Vibrationaly resolved bands beginning at energy of 9305 ± 15 cm-1 are successfully assigned to NH4NH3. These bands are ascribed to the 2 2A −1 2A transition derived from the 3...
A new time-independent perturbation theory is developed for the multireference problem. In the derivation, neither perturbed wave function nor intermediate normalization condition is required. In the single-reference case, the present approach gives the same perturbation expressions as Rayleigh–Schrödinger perturbation theory. In the multireference...
The geometrical structures of NH4 and OH3 were optimized at the MP2 level with the aug-cc-pvdz, aug-cc-pvtz, and aug-cc-pvqz basis set plus s-type diffuse functions. The adiabatic ionization potential, barrier height, and dissociation energy of NH4 and OH3 were calculated with the above basis set series and were extrapolated to the infinite basis s...
Ab initio calculations have been performed to interpret the photoelectron spectrum of gaseous cuprous chloride, Cu3Cl3. Density functional calculations revealed Cu3Cl3 to be a planar cyclic D3h molecule. Koopmans' theorem and two-hole/one-particle calculations with canonical Hartree-Fock orbitals were used to interpret the vertical ionization energ...
The structure of the CH2OH radical was optimized at the UHF, UB3LYP, and MP2 levels. The calculated ionization potential was very close to the experimental one. The transition dipole moments from the ground state to the first four lowest excited states were calculated with and without Cs symmetry using the multireference single and double configura...
The electronic structure of the whole molecule of acidic phospholipase A2 (PLA2) from the venom of Agkistrodon halys pallas (A. halys pallas) has been calculated using the extended negative factor counting (ENFC) method in which dimers were calculated at the ab initio level using a minimal basis set, with simulation of the aqueous environment. Hopp...
