Theoretical investigations of spectroscopic parameters and molecular constants for electronic ground state of Cl_2 and its isotopes

The potential energy curve of the C12 （X1∑g＋） is investigated by the highly accurate valence internally contracted multireference configuration interaction （MRCI） approach in combination with the largest correlation-consistent basis set, aug-cc-pV6Z, in the valence range. The theoretical spectroscopic parameters and the molecular constants of three isotopes, 35Cl2, 35Cl37Cl and 37Cl2, are studied. For the 35Cl2（X1∑g＋）, the values of Do, De, Re, We, we）we, ae and Be are obtained to be 2.3921 eV, 2.4264 eV, 0.19939 nm, 555.13 cm-1, 2.6772 cm-1, 0.001481 cm-1 and 0.24225 cm-1, respectively. For the 356137Cl（X1∑g＋）, the values of Do, De, Re, We, WeXe, ae and Be are calculated to be 2.3918 eV, 2.4257 eV, 0.19939 nm, 547.68 cm-1, 2.6234 cm-1, 0.00140 cm^1 and 0.23572 cm-1, respectively. And for the 37Cl2（X1∑g＋）, the values of Do, De, Re, We, WeXe, ae and Be are obtained to be 2.3923 eV, 2.4257 eV, 0.19939 nm, 540.06 cm-1, 2.5556 cm-1, 0.00139 cm-1 and 0.22919 cm-1, respectively. These spectroscopic results are in good agreement with the available experimental data. With the potential of Cl2 molecule determined at the MRCI/aug-cc-pV6Z level of theory, the total of 59 vibrational states is predicted for each isotope when the rotational quantum number J equals zero （J = 0）. The theoretical vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are determined when J = 0, which are in excellent accordance with the available experimental findings.

Molecular constants of LiCl(X^1Σ^+) and elastic collisions of two ground-state Cl and Li atoms at low and ultralow temperatures

Interaction potentials for LiCI（X^1∑＋） are constructed by the highly accurate valence internally contracted multireference configuration interaction in combination with a number of large correlation-consistent basis sets, which are used to determine the spectroscopic parameters （D0, De, Re, ωe, ωeχe, Be and αe）. The potentials obtained at the basis sets, i.e., aug-cc-pV5Z-JKFI for Cl and cc-pV5Z for Li, are selected to study the elastic collision properties of Li and Cl atoms at the impact energies from 1.0 ×10^-12 to 1.0× 10-4 a.u. The derived total elastic cross sections are very large and almost constant at ultralow temperatures, and their shapes are mainly dominated by the s-partial wave at very low impact energies. Only one shape resonance can be found in the total elastic cross sections over the present collision energy regime, which is rather strong and obviously broadened by the overlap contributions of the abundant resonances coming from various partial waves. Abundant resonances exist for the elastic partial-wave cross sections until l= 22 partial waves. The vibrational manifolds of the LiCI（X^1∑＋） molecule, which are predicted at the present level of theory and the basis sets cc-pV5Z for Li and the aug-cc-pV5Z-JKFI for Cl, should achieve much high accuracy due to the employment of the large correlation-consistent basis sets.

Spectroscopic parameters and molecular constants of HI(X^1Σ^+),DI(X^1Σ^+) and TI(X^1Σ^+) isotope molecules

The potential energy curve （PEC） of HI（X^1∑^＋） molecule is studied using the complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction approach at the correlation-consistent basis sets, aug-cc-pV6Z for H and aug-cc-pV5Z-pp for I atom. Using the PEG of HI（X^1∑^＋）, the spectroscopic parameters of three isotopes, HI（X1E＋）, DI（X^1∑^＋） and TI（X^1∑^＋）, are determined in the present work. For the HI（X^1∑^＋）, the values of Do, De, Re, ωe, ωeχe, αe and Be are 3.1551 eV, 3.2958 eV, 0.16183 nm, 2290.60 cm^-1, 40.0703 cm^-1, 0.1699 cm^-1 and 6.4373 cm^-1, respectively; for the DI （X^1∑^＋）, the values of D0, De, Re, ωe, ωeχe, αe and Be are 3.1965 eV, 3.2967 eV, 0.16183 nm, 1626.8 cm^-1, 20.8581 cm^-1, 0.0611 cm^-1 and 3.2468 cm^-1, respectively; for the TI （X^1∑^＋）, the values of Do, De, Re, ωe, ωeχe, αe and Be are of 3.2144 eV, 3.2967 eV, 0.16183 nm, 1334.43 cm^-1, 14.0765 cm^-1, 0.0338 cm^-1 and 2.1850 cm^-1, respectively. These results accord well with the available experimental results. With the PEC of HI（X^1∑^＋） molecule obtained at present, a total of 19 vibrational states are predicted for the HI, 26 for the DI, and 32 for the TI, when the rotational quantum number J is equal to zero （J = 0）. For each vibrational state, vibrational level G（v）, inertial rotation constant By and centrifugal distortion constant Dv are determined when J = 0 for the first time, which are in excellent agreement with the experimental results.

Investigations of spectroscopic parameters and molecular constants for X^1Σ_g^+, w^3△_u, and W^1△_u electronic states of P_2 molecule

The potential energy curves （PECs） of three low-lying electronic states （X1 ∑g^＋, w^3 △u, and W1 △u） of P2 molecule are investigated using the full valence complete active space self-consistent field （CASSCF） method followed by the highly accurate valence internally contracted multireference configuration interaction （MRCI） approach in conjunction with the correlation-consistent basis set in the valence range. The PECs of the electronic states involved are modified by the Davidson correction and extrapolated to the complete basis set （CBS） limit. With these PECs, the spectroscopic parameters of the three electronic states are determined and compared in detail with the experimental data. The comparison shows that excellent agreement exists between the present results and the available experimental data. The complete vibrational states are computed for the W3Au and WlAu electronic states when the rotational quantum number J equals zero and the vibrational level G（v）, the inertial rotation constant By, and the centrifugal distortion constant Dv of the first 30 vibrational states are reported, which accord well with the experimental data. The present results show that the two-point extrapolation scheme can obviously improve the quality of spectroscopic parameters and molecular constants.

Elastic Constants of Superconducting MgB2 from Molecular Dynamics Simulations with Shell Model

The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.

Constant-Volume Heat Capacity of Mixed Supercritical Fluids and Molecular Interaction in the Systems

Constant-volume heat capacities of supercritical (SC) CO2, SC CO2-n-pentane, and SC CO2-n-heptane mixtures were determined at 308.15 K in the pressure range from 6 to 12 MPa. It was found that there is a maximum in each heat capacity vs pressure curve. Intermolecular interaction in the fluids was studied.

基于分子动力学仿真的混合油中水分子扩散行为及其介电常数研究

绝缘油是油浸式变压器内绝缘的重要组成部分,其绝缘性能对电力系统的稳定运行至关重要。实验研究表明植物油与矿物油共混可有效提升其绝缘性能,但改性机理尚不明确。该文利用分子动力学研究了植物油、矿物油不同共混比例下油中水分子的扩散行为及其介电常数。结果表明:随着植物油占比增加,水分子的扩散系数逐渐降低,抑制了油中“水桥”的形成,提升了混合油的绝缘性能。水分子与混合油组分分子之间相互作用能与氢键计算结果表明,植物油中强极性基团的引入增大了混合油与水分子的相互作用能与氢键数目,抑制了水分子的热运动,导致其扩散系数降低;而随着植物油占比增加,混合油的静态介电常数显著增大,且随着含水量的提高显著上升,这是由于水分子及植物油中强极性基团的引入增大了混合油中参与极化的粒子数目,导致体系介电常数显著增高。综上所述,强极性基团是影响混合油绝缘性能的重要因素,共混时需综合考虑其对水分子扩散行为的抑制及对介电常数的增大效应,以达到提升混合油绝缘性能的目的。

MRCI study of spectroscopic and molecular properties of X^1Σ_g^+ and A^1Π_u electronic states of the C_2 radical

The potential energy curves （PECs） of X^1∑g^＋ and A^1∏u electronic states of the C2 radical have been studied using the full valence complete active space self-consistent field （CASSCF） method followed by the highly accurate valence internally contracted multireference configuration interaction （MRC1） approach in conjunction with the aug-cc-pV6Z basis set for internuclear separations from 0.08 nm to 1.66 nm. With these PECs of the C2 radical, the spectroscopic parameters of three isotopologues （^12C2, ^12C^13C and ^13C2） have been determined. Compared in detail with previous studies reported in the literature, excellent agreement has been found. The complete vibrational levels G（v）, inertial rotation constants By and centrifugal distortion constants D, for the ^12C2, ^12C^13C and ^13C2 isotopologues have been calculated for the first time for the X^1∑g^＋ and A^1∏u electronic states when the rotational quantum number J equals zero. The results are in excellent agreement with previous experimental data in the literature, which shows that the presented molecular constants in this paper are reliable and accurate.

导电石墨烯孔道内双电层结构的研究

为有效开发和利用新能源,人们迫切需要高性能的超级电容器提供能量的存储和转换.在超级电容器中双电层结构扮演着关键性的角色.本文利用分子动力学方法通过建立开放的石墨烯纳米孔道(1~2 nm),研究了KCl溶液在纳米孔道内的双电层结构,同时也比较了恒电量模拟(Q)和恒电势模拟法(U)下双电层结构的异同.结果表明在恒电势模拟法考虑了导电石墨烯壁的镜像作用使结果更符合实验中的材料系统.而石墨烯壁的镜像作用能额外吸附离子从而增强孔道内部的阴阳离子,这可能有助于电极电容的提升.通过对不同孔道高度的研究,本文发现水分子作为介电材料在水基超级电容器中发挥着决定性的作用.它能在很大程度上抵消不同离子和不同孔道高度下双电层的变化,从而在不同情况下获得了相似的电容.

Study of the Physical and Mechanical Properties of Titanium in Volume by the MEAM Method

In this work we present the results of our study on the physical and mechanical properties of titanium in volume. The work consisted in determining its physical and mechanical properties under different crystallographic structures (HCP, FCC, BCC and SC) using the Modified Embedded Atom Method (MEAM) and the MEAM potential of titanium. We used the LAMMPS calculation code, based on classical molecular dynamics, to determine the most stable structure of titanium, which is the hexagonal compact structure (HCP) with crystal parameters a = 2.952 Å and c = 4.821 Å and a cohesion energy of -4.87 eV. This structure is seconded by the cubic centred structure (BCC) with a lattice parameter a = 3.274 Å and a cohesive energy of -4.84 eV. It was shown that titanium can crystallise into a third structure which is the face-centred cubic (FCC) structure with a lattice parameter a = 4.143 Å and a cohesive energy of -4.82 eV. The results obtained in this study were compared with the theoretical results and showed considerable agreement.

CALCULATION OF THE EXCHANGE INTERACTION CONSTANT BETWEEN RARE-EARTH AND TRANSITION METAL SUBLATTICESIN R_2Fe_(17_x)Al_x(R=Tb, Gd AND Dy)COMPOUNDS

An approximate calculation of the exchange interaction constant J_(RT)between the rare-earth sublattice and the transition metal sublattice in R_2Fe_(17-x)Al_x (R= Tb,Gd, and Dy) compounds is given by the molecular-field model and the results of neutron diffraction.The calculated values, -J_(R,T)/k, for Dy_2Fe_(17-x)Al_x (x=5, 6, 7 and 8), Tb_2Fe_(10)Al_7,Gd_2Fe_(17-x)Al_x (x=7, 8) compounds are 8.62K, 8.64K, 9.52K, 10.34K and 10.66K, 10.65K, and 9.85K,respectively, they are in agreement with the experimental values, -J_(R,T)/k, of Dy_2Fe_(17-x)Al_x(x=5, 6, 7 and 8), Tb_2Fe_(10)Al_7 and Gd_2Fe_(17-x)Al_x (x=7, 8) compounds, which are 8.77K, 9.25K,10.1K, 10.9K and 10.35K, 10.1K, and 10.3K, respectively. The origins of the difference between thecalculated and the experimental results are discussed.

Molecular dynamics simulation of thermodynamic properties of YAG

In this paper we study the thermodynamic properties of Y3Al5O12 （YAG） by using molecular dynamic method combined with two- and three-body potentials. The dependences of melting process, elastic constant and diffusion coefficient on temperature of crystal YAG are simulated and compared with the experimental results. Our results show that anion O has the biggest self-diffusivity and cation Y has the smallest self-diffusivity in a crystal YAG. The calculated diffusion activation energies of ions O, Al and Y are 282.55, 439.46, 469.71kJ/mol, respectively. Comparing with experimental creep activation energy of YAG confirms that cation Y can restrict the diffusional creep rate of crystal YAG.

Molecular simulation study on K^＋-Cl^- ion pair in geological fluids

This paper reports a classical molecular dynamics study of the potential of mean forces(PMFs),association constants,microstructures K^+-Cl^- ion pair in supercritical fluids.The constrained MD method is used to derive the PMFs of K^+-Cl^- ion pair from 673 to 1273 K in low-density water(0.10-0.60 g/cm).The PMF results show that the contact ion-pair(CIP) state is the one most energetically favored for a K^+-Cl^- ion pair.The association constants of the K^+-Cl^- ion pair are calculated from the PMFs,indicating that the K^+-Cl^- ion pair is thermodynamically stable.It gets more stable as T increases or water density decreases.The microstructures of the K^+-Cl^- ion pair in the CIP and solvent-shared ion-pair states are characterized in detail.Moreover,we explore the structures and stabilities of the KCl-Au(I)/Cu(I) complexes by using quantum mechanical calculations.The results reveal that these complexes can remain stable for T up to1273 K,which indicates that KCl may act as a ligand complexing ore-forming metals in hydrothermal fluids.

植物多酚-牛血清白蛋白相互作用及对蛋白质结构的影响

多酚与蛋白质的相互作用取决于蛋白质和多酚的结构与类型,为研究不同植物多酚与牛血清白蛋白(bovine serum albumin,BSA)之间的相互作用,探明不同植物多酚对BSA结构的影响,进而筛选出稳定的植物多酚-BSA复合物。该研究采用原花青素(proanthocyanidins,PC)、儿茶素(catechin,C)、表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)、茶多酚(tea polyphenol,TP),通过紫外光谱法、荧光光谱法、红外光谱法和分子对接研究植物多酚与BSA相互作用及其对蛋白质结构的影响。结果表明:4种植物多酚-BSA复合物的紫外最大波长红移由大到小为EGCG(365 nm)、PC(364 nm)、C(364 nm)、TP(363 nm);红外光谱发现,酰胺Ⅰ带的吸收峰(1657.44 cm^(−1))发生蓝移由大到小为PC(1656.15 cm^(−1))、TP(1632.07 cm^(−1))、EGCG(1631.49 cm^(−1))、C(1631.44 cm^(−1)),烟酰胺II带峰形变宽;BSA二级结构由β-转角、无规卷曲转变为β-折叠、ɑ-螺旋,β-折叠含量增加C-BSA(40.20%)、PC-BSA(39.50%)、EGCG-BSA(39.32%)、TP-BSA(34.04%),表明C更能促进BSA的二级结构稳定;荧光光谱表明4种多酚对BSA的猝灭类型均为静态猝灭,且结合位点约为1,表明存在一个结合位点;分子对接结果表明该结合位点位于Sub-domain IIA的疏水腔中,分子间相互作用力主要是氢键、疏水作用力,结合能由小到大为C(−3.72 kJ/mol)、EGCG(−1.77 kJl/mol)、PC(−1.02 kJ/mol)、TP(−0.38 kJ/mol);4种多酚中C和EGCG与BSA相互作用程度较大,C与BSA的结合能最小,形成的复合物最稳定。通过多酚与蛋白相互作用研究,更好地发挥多酚和蛋白两种组分的功能作用,可为开发功能性多酚-蛋白质复合物产品提供参考。

含降冰片低介电透明聚酰亚胺的合成及性能

以对苯二胺(PDA)、2,2′-双(三氟甲基)-4,4′-二氨基联苯(TFDB)、降莰烷-2-螺-α-环戊酮-α′-螺-2″-降莰烷-5,5″,6,6″-四甲酸二酐(CPODA)为原料制备了一系列含降冰片基的共聚低介电常数透明聚酰亚胺薄膜材料。采用傅里叶变换红外光谱、热重分析、热机械分析、介电测试、光学测试、力学性能测试研究了TFDB中三氟甲基对合成材料综合性能的影响,同时通过分子模拟技术分析了材料微观结构,解释了性能变化的内在机理。结果表明,合成的聚酰亚胺材料已经完全亚胺化;随着TFDB物质的量分数从0%增加到40%,热失重1%温度从453℃降低到432℃,在频率为105 Hz条件下,介电常数从2.87降低到2.68,介电损耗角正切从0.007 3降低到0.004 8,截止波长从372 nm降低至361 nm;合成的材料在450 nm处的透过率均达到了85%。TFDB引入使材料拉伸性能下降,所有材料均溶解于N,N-二甲基甲酰胺和N,N-二甲基乙酰胺。分子模拟结果表明,降冰片基团中不含有苯环,缺少苯环电子共轭,在三氟甲基吸电子作用和大体积效应下,单位体积的偶极矩和极化率降低,分子链间距增大,分子间的作用力减小,聚合物的内聚能密度随之降低,聚合物的自由体积分数增加。降冰片与三氟甲基的引入可使聚酰亚胺材料的介电常数降低、光学性能得到提升,可以通过调节TFDB的含量来平衡材料的综合性能。

Optical spectroscopy of CrO and electronic states of the Cr group metal monoxides

All of the experimentally known electronic states of the Cr group metal monoxides(Cr O,Mo O,and WO)have been presented in the paper.The optical spectra of the Cr O molecule have been investigated in the gas phase through a combination of the laser-induced fluorescence(LIF)excitation and single-vibronic-level(SVL)emission spectroscopy in the supersonic expansion.The rotational constants of the vibronic electronic states,including X^(5)Π_(-1)(v=0–3),B^(5)Π_(-1)(v=0–10),and B~5Π_1(v=1,5),and the vibrational constants of the spin–orbit components X^(5)Π_(-1,0,1)have been obtained.The molecular constants of the Mo O and WO molecules have been summarized by reviewing the previous spectroscopic studies,and a comprehensive energy level diagram of the Cr group metal monoxides has been constructed.By comparing the electronic configurations,bond lengths,and vibrational frequencies of all the transition metal monoxides in the ground electronic state,the significance of the relativistic effect in the bonding of the 5d transition metal monoxides has been discussed.The related spectroscopic data of the Cr O molecule are available at https://doi.org/10.57760/sciencedb.j00113.00085.

硫化铅在19520~22900 cm^(-1)范围内振转光谱的研究

本文采用了激光消-激光诱导荧光的方法研究了硫化铅在19520~22900 cm^(-1)范围内的振转光谱.基于对测量得到的实验光谱数据分析的基础,本文确认此段光谱为硫化铅的A-X和B-X振转跃迁光谱.通过分析和讨论19520~21090 cm^(-1)范围内的光谱数据,确认该段光谱的上电子态是_(3)Π_(0+)和_(3)Σ_(0+)^(-)态的混合态.其中,^(3)Π_(0+)在该混合态中占主导地位.在22025~22900 cm^(-1)范围内的光谱属于B^(3)Π_(1)−X^(1)Σ^(+)跃迁谱.通过分析实验数据获得了这两个电子跃迁光谱的上下电子态的光谱常数.在理论方面,本文RKR/LEVEL的方法计算了这两个跃迁的振动态之间的弗兰克-康登因子.本文中对实验和计算的结果与已报道的实验和理论结果进行了对比和分析,实验确定了硫化铅的A态是一个混合态,这和Balasubramanian的相对论组态相互作用计算的结果一致,计算得到的弗兰克-康登因子和实验光谱相应跃迁的谱线强度吻合.

Assignation of Acidic Dissociation Constants of Dimethoxyphenylfluoron

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石墨烯纳米孔道内受限水介电常数影响因素的分子动力学模拟

受限水的介电特性对于石墨烯电容器的储能效率有着重大的影响.因此本文使用分子动力模方法,研究了不同石墨烯纳米孔道宽度(0.812~10 nm)下内受限水介电常数的分布及其影响因素.结果表明,在石墨烯纳米孔道内部受限水双电层结构可分为空隙层、界面层和体相层三个部分.其整体的介电常数随孔道大小的降低而线性减少.这是由内部体相层的宽度的降低而导致的.此外电极电压大小和石墨烯-水相互作用参数εCO的强弱也会显著改变电极表面的双电层(Electric Double Layers,EDLs)结构.其中电压的增大使得介电常数分布的震荡的程度也随之增加,最终导致了整体介电常数的减小.与之类似,亲水态的石墨烯表面(高εCO)下受限水分布的震荡程度也显著增加,这导致了整体介电常数的降低.

I_(2)-IR配体双环α-亚氨基膦酸酯定量构效关系研究

咪唑啉I 2受体(I_(2)-IR)对阿尔茨海默症(AD)和其他神经退行性疾病的治疗具有重要意义。为获得更高活性的I_(2)-IR配体,采用比较分子场(CoMFA)和比较分子相似性指数分析(CoMSIA)方法,为新型I_(2)-IR配体双环α-亚氨基膦酸酯类化合物构建了合理的三维定量构象关系(3D-QSAR)模型。结果显示CoMFA和CoMSIA模型具有良好的稳定性和预测能力。根据3D-QSAR模型分析结果进行分子设计并完成活性预测,预测结果印证了分析的合理性,为该系列化合物的结构优化提供了合理建议。