HOF分子非谐性力场、光谱常数和振动能级的迭代三激发耦合簇计算

采用包含迭代三激发的耦合簇理论（ CC3和CCSDT-3）,在aug-cc-pVTZ基组水平上对HOF分子几何构型进行优化。通过解析二阶导数结合有限差分技术获得HOF二阶、完全三阶和半对角四阶力场。通过非谐性分析,得到其基频、旋振相互作用常数、非谐性常数和离心畸变光谱常数。应用二阶振动微扰理论（VPT2）得到HOF多个泛频峰位置。目前计算值与实验及其它文献结果符合良好。     

HOF分子非谐性力场、光谱常数和振动能级的迭代三激发耦合簇计算

采用包含迭代三激发的耦合簇理论(CC3和CCSDT-3), 在aug-cc-pVTZ基组水平上对HOF分子几何构型进行优化. 通过解析二阶导数结合有限差分技术获得HOF二阶、完全三阶和半对角四阶力场. 通过非谐性分析, 得到其基频、旋振相互作用常数、非谐性常数和离心畸变光谱常数. 应用二阶振动微扰理论(VPT2)得到HOF多个泛频峰位置. 目前计算值与实验及其它文献结果符合良好.     

六次非简谐振子的多尺度微扰理论

应用多尺度微扰理论, 对于弱耦合常数的六次非简谐振子得到了其运动方程的经典和量子情况下的一阶解. 与Taylor级数解不同的是, 无论是在经典和量子解中频率移动出现在各阶表达式中, 因此多尺度微扰理论是优于Taylor级数解的一种处理弱耦合常数非简谐振动的近似方法.     

广义非简谐振子的多尺度微扰理论

应用多尺度微扰理论到广义非简谐振子, 得到了一阶经典和量子微扰解. 特别是 我们的量子解在极限条件下能方便地转变为经典解, 并且坐标和动量算符的对易 关系的简化十分自然. 与Taylor级数解相比较, 无论是在经典还是在量子解 中频率移动都出现在各阶振动表达式中, 所以多尺度微扰解是弱耦合非简谐振动的较好解法.     

Anharmonic Analysis of the Vibrational States of Phenyldichlorarsine and Phenyldichlorphosphine

Using the DFT/B3LYP method with the basis set 6-31G*(**), we analyzed the vibrational spectra of the conformers phenyldichlorarsine and phenyldichlorphosphine in the anharmonic approximation. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 557–559, July–August, 2005.     

Rovibrational and energetic analysis of the hydroxyethynyl anion (CCOH−)

For the first time, high-level structural and rovibrational data are provided for the hyroxyethynyl anion, CCOH^?. CCOH^? is a promising molecule for interstellar detection even though no new anions have been observed in the interstellar medium for the past half-decade. The large dipole moment of the corresponding neutral radical may be key for its creation as has been hypothesised and supported for other anions known to exist in various astronomical environments. Highly accurate quartic force fields are employed where previous benchmarks have produced spectroscopic constants and anharmonic vibrational frequencies within 20 MHz and 1 cm^?1, respectively, of experiment. This same approach is applied here for CCOH^? and its deuterated isotopologue with the goal of assisting laboratory experiments and/or astronomical observers in the potential detection of this anion.     

High-level theoretical spectroscopic parameters for three ions of astrochemical interest

The equilibrium geometry and rovibrational spectroscopic parameters of the three astrochemical ions l-C₃H⁺, l-SiC₂H⁺, and C₃N^? and some of their isotopologues are obtained from high-level quantum chemical calculations. A composite approach based on the explicitly correlated coupled-cluster method CCSD(T)-F12b, that further includes core correlation, scalar-relativistic effects and most importantly higher order correlation beyond CCSD(T) is used to set-up the near-equilibrium potential energy surface (PES). The spectroscopic parameters of these linear tetra-atomic ions are then extracted from these PESs by vibrational perturbation theory of second order (VPT2). Calculation of absolute intensities is also carried out for the stretching frequencies of the cations in order to identify the bands that are most likely to be detected. The importance of the accurate calculation of the rotational constants B₀ and D₀ for astrochemistry is discussed as well as the limits of VPT2 in this context and reasons for these limitations.     

Anharmonic force constants of GaSb from the measured third order elastic constants at 300°K

The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 10¹¹ N.m.⁻², are C_l11 = ™ 4 ·75 ± 0·06 C₁₄₄ = + 0·50 ± 0·25 C₁₁₃ = ™ 3 ·08 ± 0·02 C₁₆₆ = ™ 2·16 ± 0·13 C₁₂₃ = ™ 0 ·44 ± 0·29 C₄₅₆ = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 10¹¹ N.m⁻²)γ=− 2·406;δ=0·407;ε=−0·222.     

Synthesis and Raman spectroscopic characterisation of the oxalate mineral wheatleyite Na2Cu2+(C2O4)2·2H2O

The mineral wheatleyite has been synthesised and characterised by Raman spectroscopy complimented with infrared spectroscopy. Two Raman bands at 1434 and 1470 cm⁻¹ are assigned to the ν_{(C O)} stretching mode and implies two independent oxalate anions. Two intense Raman bands observed at 904 and 860 cm⁻¹ are assigned to the ν(C C) stretching mode and support the concept of two non‐equivalent oxalate units in the wheatleyite structure. Two strong bands observed at 565 and 585 cm⁻¹ are assigned to the symmetric CCO in plane bending modes. The Raman band at 387 cm⁻¹ is attributed to the CuO stretching vibration and the bands at 127 and 173 cm⁻¹ to OCuO bending vibrations. A comparison is made with Raman spectra of selected natural oxalate bearing minerals. Oxalates are markers or indicators of environmental events. Oxalates are readily determined by Raman spectroscopy. Thus, deterioration of works of art, biogeochemical cycles, plant metal complexation, the presence of pigments and minerals formed in caves can be analysed. Copyright © 2008 John Wiley & Sons, Ltd.     

HNCS分子的光谱常数和非谐振力场的理论研究

采用Gaussian09数据包,以密度泛函理论（B3LYP、B3PW91）和二阶微扰（MP2）方法,分别采用基组6-311+G、6-311++G(2d,2p)、cc-PVNZ(N=T,Q)以及加入弥散函数的高角动量基组aug-cc-PVNZ(N=T,Q)等计算了HNCS分子的光谱常数和非谐振力场。结果表明：B3LYP、B3PW91和MP2计算的结果与实验结果都比较接近;当基组由VTZ增大到VQZ或加弥散函数对结果的影响均不明显;其中B3PW91\cc-PVTZ的各项计算结果相对于其他计算结果更接近实验值。通过计算,可以在前人基础上进一步预测HNCS分子其它的光谱常数（如:非谐性常数、科里奥利耦合常数等）。     

HNCS分子的光谱常数和非谐振力场的理论研究

采用Gaussian09数据包,以密度泛函理论(B3LYP、B3PW91)和二阶微扰(MP2)方法,分别采用基组6-311+G、6-311++G(2d,2p)、cc-PVNZ(N=T,Q)以及加入弥散函数的高角动量基组aug-ccPVNZ(N=T,Q)等计算了异磺氰酸(HNCS)分子的光谱常数和非谐振力场.结果表明:B3LYP、B3PW91和MP2计算的结果与实验结果都比较接近;当基组由VTZ增大到VQZ或加弥散函数对结果的影响均不明显;其中B3PW91/cc-PVTZ的各项计算结果相对于其他计算结果更接近实验值.通过计算,可以在前人基础上进一步预测HNCS分子其它的光谱常数(如:非谐性常数、科里奥利耦合常数等).     

Experimental and theoretical studies of the vibrational spectra of CHD2Br

The dideuterated form of methyl bromide, CHD₂Br, has been synthesized and the gas-phase infrared spectra investigated in the range 400–10,000?cm^–1 using a medium-resolution FTIR spectrometer. The nine fundamental bands have been characterized in detail. Six of them, i.e. ν ₁, ν ₄, ν ₅, ν ₇, ν ₈ and ν ₉, have been rotationally analysed through the assignment of the partially resolved structure of the ^PQ_K and ^RQ_K cluster of lines and the spectroscopic parameters have been derived in the symmetric top limit approximation. Among the fundamental levels, anharmonic resonance occurs between ν ₇/ν ₄?+?ν ₈ and ν ₈/ν ₆?+?ν ₉. An isotopic ^79/81Br shift was found for ν ₆ and in the more complex region of the ν ₈ fundamental. High-quality ab initio calculations – carried out at coupled cluster level [CCSD(T)] employing the correlation-consistent basis set of Dunning (cc-pVTZ) – were performed to determine quadratic, cubic and quartic (semidiagonal) force constants. Using these constants and applying second-order vibrational perturbation theory (VPT2), with allowance for resonances (when necessary), permitted us to identify and assign, in addition to the fundamentals, about 70 overtones and combination bands up to three quanta.     

On the One-Dimensional Transition State Theory and the Relation between Statistical and Deterministic Oscillation Frequencies of Anharmonic Energy Wells

The transition state theory allows the development of approximated models useful to study the non-equilibrium evolution of systems undergoing transformations between two states (e.g., chemical reactions). In a simplified 1D setting, the characteristic rate constants are typically written in terms of a temperature-dependent characteristic oscillation frequency ${\nu }_s$, describing the exploration of the phase space. As a particular case, this statistical oscillation frequency ${\nu }_s$ can be defined for an arbitrary convex potential energy well. This value is compared here with the deterministic oscillation frequency ${\nu }_d$ of the corresponding anharmonic oscillator. It is proved that there is a universal relationship between statistical and deterministic frequencies, which is the same for classical and relativistic mechanics. The independence of this relationship from the adopted physical laws gives it an interesting thermodynamic and pedagogical meaning. Several examples clarify the meaning of this relationship from both physical and mathematical viewpoints.     

PO2自由基的光谱常数和非谐力场的理论研究

利用B3PW91、B3LYP和B3P86方法以及cc-pvQz和6-311++G(3df,3pd)基组计算了PO2自由基的光谱常数。先将计算的平衡几何结构、转动常数、谐频和基频、四次离心畸变常数和六次离心畸变常数与已有的相应实验或理论数据进行了比较。在此基础上,从理论上预测了非谐性常数、振转相互作用常数、科里奥利耦合常数、三次和四次力常数。计算结果表明,B3PW91/G理论水平得到的PO2自由基的光谱常数是可靠的。     

A heteronuclear intermolecular single-quantum coherence scheme for high-resolution 2D J-resolved 1H NMR spectra in inhomogeneous magnetic fields

Based on heteronuclear intermolecular single-quantum coherences between proton (¹H) and quadrupolar nuclei (i.e. deuterium ²H), a three-dimensional nuclear magnetic resonance (NMR) pulse sequence is proposed for recovering high-resolution two-dimensional J-resolved NMR spectra from samples mixed with a deuterated solvent in the presence of large magnetic field inhomogeneities. Benefitting from excitation of spins via two different radio frequency (RF) transmit channels, this sequence is suitable for applications in randomly large inhomogeneous fields and the solvent suppression generally required in homonuclear intermolecular multiple-quantum coherence approaches is no longer necessary. Systematic theoretical analyses are given based on the distant dipolar field treatment. Experiment on a sample of corn oil in deuterated acetone and ethyl 3-bromopropionate and acetone dissolved in DMSO-d₆ in a deshimmed field with severe inhomogeneous broadening is performed to show the feasibility and applicability of this sequence.     

Anharmonic force field and equilibrium structure of nitric acid

The quadratic, cubic and semi-diagonal quartic force field of nitric acid has been calculated at the CCSD(T) level of theory employing a basis set of triple-ζ quality. A semi-experimental equilibrium structure has been derived from experimental ground state rotational constants and rovibrational interaction parameters calculated from the ab initio force field. It is found that the A and B semi-experimental equilibrium rotational constants of the ¹⁸O isotopologues (for which the rotation of principal axes is large) cannot be accurately reproduced. This problem is discussed and a remedy is proposed. Finally, the semi-experimental structure is in agreement with the ab initio structure calculated at the CCSD(T) level of theory using a basis set of at least quadruple-ζ quality and a core correlation correction, except for the long NO single bond for which the CCSD(T) value is too short due to inadequate treatment of electron correlation. The empirical structures are also determined and their accuracy is discussed. The best equilibrium structure is: r_e(NO_syn) = 1.209(1) Å, r_e(NO_anti) = 1.194(1) Å, r_e(NO) = 1.397(1) Å, r_e(OH) = 0.968(1) Å, ∠(ONO_syn) = 115.8(1)°, ∠(ONO_anti) = 114.2(1)° and ∠(NOH) = 102.2(1)°.     

Recent progress in molecular simulation of aqueous electrolytes: force fields,chemical potentials and solubility

Although aqueous electrolytes are among the most important solutions, the molecular simulation of their intertwined properties of chemical potentials, solubility and activity coefficients has remained a challenging problem, and has attracted considerable recent interest. In this perspectives review, we focus on the simplest case of aqueous sodium chloride at ambient conditions and discuss the two main factors that have impeded progress. The first is lack of consensus with respect to the appropriate methodology for force field (FF) development. We examine how most commonly used FFs have been developed, and emphasise the importance of distinguishing between ‘Training Set Properties’ used to fit the FF parameters, and ‘Test Set Properties’, which are pure predictions of additional properties. The second is disagreement among solubility results obtained, even using identical FFs and thermodynamic conditions. Solubility calculations have been approached using both thermodynamic-based methods and direct molecular dynamics-based methods implementing coexisting solution and solid phases. Although convergence has been very recently achieved among results based on the former approach, there is as yet no general agreement with simulation results based on the latter methodology. We also propose a new method to directly calculate the electrolyte standard chemical potential in the Henry law ideality model. We conclude by making recommendations for calculating solubility, chemical potentials and activity coefficients, and outline a potential path for future progress.     

由热学性质获取氩晶体原子间各阶力常数

本文基于晶格动力学和量子力学微扰理论推导了氩晶体的热膨胀系数和比热与原子间相互作用的各阶力常数之间的关系公式,在此基础上根据热膨胀系数和比热的数据计算了氩晶体内的原子间相互作用的各阶力常数,并根据这些力常数绘制了原子间相互作用势能曲线,经比对发现该势能曲线与Morse势能曲线能较好吻合,这表明,本文提出的从热膨胀系数和比热获取各阶力常数的方法是正确的。