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Ab initio Predictions of Structural and Thermodynamic Properties of Zr2AlC Under High Pressure and High Temperature 下载免费PDF全文
The structural and thermodynamic properties of Zr2AlC at high pressure and high temperature are investigated by first principles density functional theory method. The calculated lattice parameters of Zr2AlC are in good agreement with the available theoretical data. The pressure dependences of the elastic constants, bulk modulus, shear modulus, Young's modulus, and Vickers hardness of Zr2AlC are successfully obtained. The elastic anisotropy is examined through the computation of the direction dependence of Young's modulus. By using the quasiharmonic Debye model, the thermodynamic properties including the Debye temperature, heat capacity, volume thermal expansion coefficient, and Grüneisen parameter at high pressure and temperature are predicted for the first time. 相似文献
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Substituent Effect on Infrared Spectra and Thermodynamic Properties of Polynitroamino Substituted Cyclopentane and Cyclohexane 下载免费PDF全文
Density functional theory method was employed to study the effect of the nitroamino group as a substituent in cyclopentane and cyclohexane, which usually construct polycyclic or caged nitramines. Based on the optimized molecular structures of two groups of monocyclic nitramines at the B3LYP/6-31G** level, the infrared (IR) spectra were obtained and assigned by harmonic vibrational analysis. The calculated results agree reasonably with the available experimental data. According to the principles of statistic thermodynamics, thermodynamic properties were derived from the IR spectra, which were linearly correlated with the number of nitroamino groups as well as the temperature. The. 相似文献
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运用密度泛函理论中广义梯度近似(GGA)的VWN-BP方法结合周期性平板模型, 研究N2在UO(100)表面的吸附. 研究表明, N2平行吸附在UO(100)表面穴位为最稳定吸附构型, 吸附能为79.0 kJ·mol-1. Mulliken布居分析显示, N2获得电子. 吸附后, N—N伸缩振动频率发生红移, 波数在1770-2143 cm-1之间. 态密度分析表明, U原子将d、f电子转移至N2的2π轨道. 计算所得解离反应的能垒为266.9 kJ·mol-1. 相似文献
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丁二酰亚胺的结构、振动频率和热力学性质计算 总被引:2,自引:0,他引:2
用密度泛函理论(DFT)和从头计算(ab initio)方法,在B3LYP/6-31G、B3LYP/6-311G和MP2/6-311G水平上,全优化计算了了二酰亚胺的分子几何构型和电子结构.进行了简正振动频率分析并用校正后的频率计算了200-600K温度范围的标准热力学函数,对计算结果进行了比较和讨论. 相似文献
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采用量子化学中的密度泛函理论(DFT),在B3LYP/6-311 G(3df,2p)水平上全优化得到了单卤代二硫烷HSSX(X-H,F,Cl,Br)链型和分叉型两种异构体的平衡结构。计算结果表明.在热力学上,所有链型的HSSX为稳定构型.其能量分别较分叉型构型低109.8、60.2、74.8和73.1kJ/mol。同时,采用统计热力学方法,研究了两种平衡结构之间相互转化的化学热力学性质,发现异构化反应的平衡常数很小。 相似文献
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1N‐Phenyl‐3‐(2,4‐dichlorophenyl)‐5‐(4‐chlorophenyl)‐2‐pyrazoline has been synthesized and characterized by elemental analysis, IR, UV‐Vis and X‐ray single crystal diffraction. Density functional calculations have been carried out for the title compound by using the B3LYP method with a 6‐311G** basis set. The calculated results show that the predicted geometry can reproduce well the structural parameters. The electronic absorption spectra calculated in the gas phase are better than those calculated in EtOH solvent to model the experimental electronic spectra. Natural Bond Orbital (NBO) analyses suggest that the above electronic transitions are mainly assigned to π → π* transitions. On the basis of vibrational analyses, the thermodynamic properties of the compound at different temperatures have been calculated, revealing the correlations between C0p, m, S0m, H0m and temperature. 相似文献
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Elastic Tensor and Thermodynamic Property of Magnesium Silicate Perovskite from First-principles Calculations 下载免费PDF全文
Zi-jiang Liu Xiao-wei Sun Cai-rong Zhang Jian-bo Hu Ting Song Jian-hong Qi 《化学物理学报(中文版)》2011,24(6):703-710
The thermodynamic and elastic properties of magnesium silicate (MgSiO3) perovskite at high pressure are investigated with the quasi-harmonic Debye model and the first-principles method based on the density functional theory. The obtained equation of state is consis-tent with the available experimental data. The heat capacity and the thermal expansion coefficient agree with the observed values and other calculations at high pressures and tem-peratures. The elastic constants are calculated using the finite strain method. A complete elastic tensor of MgSiO3 perovskite is determined in the wide pressure range. The geo-logically important quantities: Young's modulus, Poisson's ratio, Debye temperature, and crystal anisotropy, are derived from the calculated data. 相似文献
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Density Functional Theory Study on Electronic and Magnetic Properties of Mn-doped (MgO)n (n=2-10) Clusters 下载免费PDF全文
We study the geometries, stabilities, electronic and magnetic properties of (MgO)n (n=2-10) clusters doped with a single Mn atom using the density functional theory with the gener-alized gradient approximation. The optimized geometries show that the impurity Mn atom prefers to replace the Mg atom which has low coordination number in all the lowest-energy MnMgn-1On (n=2-10) structures. The stability analysis clearly represents that the aver-age binding energies of the doped clusters are larger than those of the corresponding pure (MgO)n clusters. Maximum peaks of the second order energy differences are observed for MnMgn-1On clusters at n=6, 9, implying that these clusters exhibit higher stability than their neighboring clusters. In addition, all the Mn-doped Mg clusters exhibit high total magnetic moments with the exception of MnMgO2 which has 3.00 μB. Their magnetic be-havior is attributed to the impurity Mn atom, the charge transfer modes, and the size of MnMgn-1On clusters. 相似文献
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Xuefei Zhao Ping Lü Ce Hao Shenmin Li Jieshan Qiu 《Journal of Molecular Structure》2006,760(1-3):53-57
Hydrogen and fluorine addition reactions with C28(Td) have been investigated by the density function theory method at B3LYP/6-31G level. The interaction potential between C28(Td) and atom X (X=H and F) shows that there are three possible stable isomers of C28(Td)X (X=H and F) and the average binding energy calculations suggest that C28(Td)H4 is the most stable hydrogen adduct among C28(Td)Hn (n=1–28). Furthermore, by comparisons of the energy between C28(Td)H and C28(Cs)H we found that the former are more stable than the later, and the structural and energy analysis further indicate that C28(Cs)H is only with a small distortion of C28(Td)H symmetry. In addition, the transition states, as well as reaction pathways of X transfer reactions between different key points on C28(Td) representative patch are given to explore the possible reaction mechanism. 相似文献
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氟、氯和甲基取代丁二酰亚胺的结构、红外光谱和热力学性质的密度泛函理论研究 总被引:2,自引:0,他引:2
用密度泛函理论(DFT)的B3LYP方法(6-31G*基组),计算研究了丁二酰亚胺(SIM)的氟、氯和甲基取代物(SIMF,SIMCl和SIMMe)的几何构型、电子结构、红外光谱和热力学性质,讨论了取代基效应.结果表明,SIMF和SIMCl均为平面构型,SIMMe接近平面构型.羰基伸缩振动频率(νC=O)均分裂为两个谱带,低频带出现在1734~1771cm-1,高频带出现在1792~1822cm-1,且前者强于后者.与SIM相比,吸电子基(F和Cl)使νC=O和偶极矩增大,推电子基(CH3)的影响正相反.由校正频率计算了298~800K温度范围的热力学性质熵(S°)和热容(Cp°). 相似文献
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对萤火虫氧化荧光素(S)-2-(6-羟基-2-苯并噻唑基)-2-噻唑啉-4-酮(BTZ)中苯并噻唑环的N和S原子进行取代, 形成一系列萤火虫氧化荧光素类似物, 并采用TD B3LYP/6-31+G(d)方法, 通过计算氧化物中性态与羟基去质子化后的负一价态在气相、水溶液和模拟生物环境下的吸收与发射光谱, 讨论环内不同取代原子对光谱的影响. 结果表明, X1位以O原子取代S原子的化合物的最大吸收值发生蓝移, 以N原子取代S原子的化合物的最大吸收值发生红移. 去质子化可增加苯环上π轨道成份, 降低能隙, 从而有利于提高电子跃迁几率, 使荧光发射波长红移; 通过取代X1和X2位杂原子, 可调节发射光谱红移达44 nm, 蓝移达41 nm(在模拟蛋白中). 6种化合物荧光发光范围较宽, 振子强度较大, 可以作为潜在的化学发光材料用于生物成像研究. 相似文献
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A calorimetric and thermodynamic investigation of two alkali-metal uranyl molybdates with general composition A2[(UO2)2(MoO4)O2], where A = K and Rb, was performed. Both phases were synthesized by solid-state sintering of a mixture of potassium or rubidium nitrate, molybdenum (VI) oxide and gamma-uranium (VI) oxide at high temperatures. The synthetic products were characterised by X-ray powder diffraction and X-ray fluorescence methods. The enthalpy of formation of K2[(UO2)2(MoO4)O2] was determined using HF-solution calorimetry giving ΔfH° (T = 298 K, K2[(UO2)2(MoO4)O2], cr) = −(4018 ± 8) kJ · mol−1. The low-temperature heat capacity, Ср°, was measured using adiabatic calorimetry from T = (7 to 335) K for K2[(UO2)2(MoO4)O2] and from T = (7 to 326) K for Rb2[(UO2)2(MoO4)O2]. Using these Ср° values, the third law entropy at T = 298.15 K, S°, is calculated as (374 ± 1) J · K−1 · mol−1 for K2[(UO2)2(MoO4)O2] and (390 ± 1) J · K−1 · mol−1 for Rb2[(UO2)2(MoO4)O2]. These new experimental results, together with literature data, are used to calculate the Gibbs energy of formation, ΔfG°, for both phases giving: ΔfG° (T = 298 K, K2[(UO2)2(MoO4)O2], cr) = (−3747 ± 8) kJ · mol−1 and ΔfG° (T = 298 K, Rb2[(UO2)2(MoO4)], cr) = −3736 ± 5 kJ · mol−1. Smoothed Ср°(Т) values between 0 K and 320 K are presented, along with values for S° and the functions [H°(T) − H°(0)] and [G°(T) − H°(0)], for both phases. The stability behaviour of various solid phases and solution complexes in the (K2MoO4 + UO3 + H2O) system with and without CO2 at T = 298 K was investigated by thermodynamic model calculations using the Gibbs energy minimisation approach. 相似文献
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Zhou Shiqi 《化学物理学报(中文版)》2005,18(5):679-688
A universal theoretical framework is proposed for calculating potential of mean force (PMF) between two solute particles immersed in a solvent bath, the present method overcomes all of drawbacks of previous methods. The only input required to implement the recipe is solvent density distribution profile around a single solute particle. The universal framework is applied to calculate the PMF between two large spherical particles immersed in small hard sphere solvent bath. Comparison between the present predictions and existing simulation data shows reliability of the present recipe. Effects of solvent-solute interaction detail, solvent bulk density, and solute size on the excess PMF are investigated. The resultant conclusion is that depletion of solvent component by the solute particle induces attractive excess PMF, while gathering of solvent component by the solute particle induces repulsive excess PMF, high solvent bulk density and large solute size can strengthen the tendency of attraction or repulsion. Relevance of transition from depletion attraction to gathering repulsion with the biomolecular interaction, i.e. hydrophobic attraction and hydration repulsion, is discussed. 相似文献
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