Transport Properties of Simple Fluids from the Soft‐Core Double Yukawa Potential

The present work is concerned with checking a new and simple pair potential function (soft‐core double Yukawa potential) for noble gases by calculation of the transport properties. The viscosity, thermal conductivity and self diffusion coefficient in dilute gas limit in the temperature range of 298‐1400 K are calculated and agreement with the measurements is, in general, within the experimental error. A comparison of the calculated and experimental values of the viscosity, thermal conductivity and the diffusion coefficients yields an average absolute deviation of 0.5%, 1.5% and 1.2%, respectively. Also, the calculated transport properties from this potential have been compared with those calculations via the accurate experimental potential and also the corresponding state.     

用密度梯度理论研究缔合流体的汽液成核性质

在密度梯度展开的基础上,将影响参数k 表达成温度的函数,建立了一个适用于均相和非均相缔合流体的状态方程。应用流体的蒸汽压和液相密度实验数据关联分子参数。在密度梯度理论的框架下,计算了水,重水,甲醇,乙醇,正丙醇,正丁醇,正戊醇和正己醇的成核速率并与实验数据进行了对比,计算结果令人满意。结果表明,密度梯度理论与密度泛函理论一样,可研究液核的结构和性质,但通过调整影响参数k, 可获得更为准确的成核速率。     

Viscosity Prediction for Oxygen,Nitrogen and Their Mixtures at Zero and Moderately Dense Regimes via Semi‐Empirically Based Assessment

The viscosity coefficients for the gaseous states of N₂ and O₂ and their mixtures are determined at zero and moderately density regimes. The Lennard‐Jones 12–6 (LJ 12–6) potential energy function is used as the initial model potential required y the technique. The interaction potential energies from the inversion procedure reproduce the viscosity commensurate to the best measurements. The initial density dependence of gaseous viscosity coefficient according to the Rainwater‐Friend theory, which was given by Najafi et al., has been considered for pure N₂ and pure O₂.     

Density Functional Theory Studies on Intermolecular Interactions of 4‐Amino‐3,5‐dinitropyrazole with NH3 and H2O

Density functional theory (DFT) method with 6‐311++G** basis set was applied to study intermolecular interactions of 4‐amino‐3,5‐dinitropyrazole (LLM‐116)/NH₃ and LLM‐116/H₂O supermolecules. Four optimized stable supermolecules were found on the potential energy surface. The intermolecular interaction energy was calculated with basis set superposition error (BSSE) correction and zero point energy (ZPE) correction. The greatest corrected intermolecular interaction energies of LLM‐116/NH₃ and LLM‐116/H₂O supermolecules are –42.75 and –19.09 kJ×mol^‐1 respectively, indicating that the intensity of interaction between LLM‐116 and NH₃ is stronger than that of LLM‐116/H₂O. The intermolecular interaction is an exothermic process accompanied by a decrease in the probability of supermolecules formation, and the interactions become weak as temperature increase. Natural bond orbital (NBO) analysis was performed to reveal the origin of interaction. The IR spectra were obtained and assigned by vibrational analysis. Based on vibrational analysis, the changes of thermodynamic properties from LLM‐116 to supermolecules with temperature ranging from 200.0 to 400.0 K were obtained using statistical thermodynamic method.     

微孔中简单流体粘度的分子动力学模拟及关联模型

用分子动力学模拟计算了微孔介质中流体氩在不同温度、不同密度和不同孔径下的剪切粘度.并根据Chapman-Enskog关于硬球流体传递性质的理论以及Heyes的关于Lennard-Jones流体粘度的表达式,提出了两个描述微孔介质中流体粘度的模型,该模型可以计算微孔中流体氩在不同状态下的粘度值.通过与计算机模拟值的比较,证明这两个微孔流体粘度模型是可用的.     

Combined experimental and computational modeling studies on 4‐[(2‐hydroxy‐3‐methylbenzylidene) amino]‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one

The Schiff base compound, 4‐[(2‐hydroxy‐3‐methylbenzylidene)amino]‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one, has been synthesized and characterized by IR, UV–vis, and X‐ray single‐crystal determination. Molecular geometry from X‐ray experiment of the title compound in the ground state have been compared using the density functional method (B3LYP) with 6‐31G(d,p) basis set. Calculated results show that density functional theory (DFT) can well reproduce the structure of the title compound. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6‐31G(d,p) basis set by applying the Onsager and the polarizable continuum model (PCM). The results obtained with these methods reveal that the PCM method provided more stable structure than Onsager's method. By using TD‐DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD‐DFT method and the experimental one is determined. The predicted nonlinear optical properties of the title compound are much greater than ones of urea. In addition, DFT calculations of the title compound, molecular electrostatic potential and NBO analysis were performed at B3LYP/6‐31G(d,p) level of theory. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Calculation of excited‐state ionization potential for boron‐like sequence

Excited‐state ionization potentials for boron‐like sequence with Z = 5–19 are studied systematically, using the weakest bound electron potential model theory (WBEPM theory) and iso‐spectrum‐level series conception. Nonrelativistic ionization energy is derived from the theory. Relativistic effects are included in the Breit–Pauli approximation. Comparison of the calculated excited‐state ionization potential with available experimental data is carried out for 1s²2s²2p ²P, 1s²2s²3s ²S_1/2, 1 s²2s²3p ²P, 1s²2s²3d ²D_5/2, 1s²2s²4d ²D_5/2, 1s²2s²5d ²D_5/2, and 1s²2s²6d ²D_5/2 series. The present results depart from experimental results by no more than 0.133 eV for all 81 results for which experimental data are available. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Theoretical studies on the formation mechanism and explosive performance of nitro‐substituted 1,3,5‐triazines

To develop new highly energetic materials, we have considered the design of molecules with high nitrogen content. Possible candidates include 1,3,5‐triazine derivatives. In this work, we studied potential synthetic routes for melamine using the MP2/6‐31+G(d,p)//B3LYP/6‐31G(d) level of theory. The mechanisms studied here are stepwise mechanism beginning with the dimerization of cyanamide and one‐step termolecular mechanism. The same type of mechanism is also applied to nitro‐substituted 1,3,5‐triazines. Values for the heat of formation in the solid phase were predicted from density functional theory calculations. Densities were estimated from a regression equation obtained by molecular surface electrostatic potentials. The Cheetah program was used to study the explosive performance of these compounds. In this study, we found that the explosive properties of 2‐amino‐4, 6‐dinitro‐1, 3,5‐triazine (ADNTA), and 2,4,6‐trinitro‐1,3,5‐triazine (TNTA) are similar to those of RDX and HMX, respectively. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

The exact Fermi potential yielding the Hartree–Fock electron density from orbital‐free density functional theory

The exact expression for the Fermi potential yielding the Hartree–Fock electron density within an orbital‐free density functional formalism is derived. The Fermi potential, which is defined as that part of the potential that depends on the particles’ nature, is in this context given as the sum of the Pauli potential and the exchange potential. The exact exchange potential for an orbital‐free density functional formalism is shown to be the Slater potential.     

4-羟甲基吡啶－水红移氢键的密度泛函理论研究

使用密度泛函理论B3LYP方法和6-311++G**基函数对4-羟甲基吡啶与水形成的1:1和1:2（摩尔比）氢键复合物进行了理论计算研究,分别得到稳定的4-羟甲基吡啶－H₂O和4-羟甲基吡啶－(H₂O)₂氢键复合物3个和8个。经基组重叠误差和零点振动能校正后,最稳定的1:1和1:2氢键复合物的相互作用能分别为-20.536和-44.246 kJ/mol。振动分析显示O-H···N(O)氢键的形成使复合物中O-H键对称伸缩振动频率红移(减小)。自然键轨道分析表明,4-羟甲基吡啶与水形成最稳定的1:1和1:2氢键复合物时,分子间电荷转移分别为0.02642 e 和0.03813 e 。含时密度泛函理论TD-B3LYP/ 6-311++G**计算显示,相对于4-羟甲基吡啶单体分子,氢键H-OH···N和H-OH···OH的形成分别使最大吸收光谱波长兰移8~16纳米和红移4~11纳米。     

Alternative Representations of the Correlation Energy in Density‐Functional Theory: A Kinetic‐Energy Based Adiabatic Connection

The adiabatic‐connection framework has been widely used to explore the properties of the correlation energy in density‐functional theory. The integrand in this formula may be expressed in terms of the electron–electron interactions directly, involving intrinsically two‐particle expectation values. Alternatively, it may be expressed in terms of the kinetic energy, involving only one‐particle quantities. In this work, we explore this alternative representation for the correlation energy and highlight some of its potential for the construction of new density functional approximations. The kinetic‐energy based integrand is effective in concentrating static correlation effects to the low interaction strength regime and approaches zero asymptotically, offering interesting new possibilities for modeling the correlation energy in density‐functional theory     

Density Functional Theory Investigation on the Second‐Order Nonlinear Optical Properties of Chlorobenzyl‐o‐Carborane Derivatives

The structures and second‐order nonlinear optical (NLO) properties of a series of chlorobenzyl‐o‐carboranes derivatives ( 1 – 12 ) containing different push‐pull groups have been studied by density functional theory (DFT) calculation. Our theoretical calculations show that the static first hyperpolarizability (β_tot) values gradually increase with increasing the π‐conjugation length and the strength of electron donor group. Especially, compound 12 exhibits the largest β_tot (62.404×10^?30 esu) by introducing tetrathiafulvalene (TTF), which is about 76 times larger than that of compound 1 containing aryl. This means that the appropriate structural modification can substantially increase the first hyperpolarizabilities of the studied compounds. For the sake of understanding the origin of these large NLO responses, the frontier molecular orbitals (FMOs), electron density difference maps (EDDMs), orbital energy and electronic transition energy of the studied compounds are analyzed. According to the two‐state model, the lower transition energy plays an important role in increasing the first hyperpolarizability values. This study may evoke possible ways to design preferable NLO materials.     

Advancing the Electrochemistry of the Hydrogen‐Evolution Reaction through Combining Experiment and Theory

The electrocatalytic hydrogen‐evolution reaction (HER), as the main step of water splitting and the cornerstone of exploring the mechanism of other multi‐electron transfer electrochemical processes, is the subject of extensive studies. A large number of high‐performance electrocatalysts have been developed for HER accompanied by recent significant advances in exploring its electrochemical nature. Herein we present a critical appraisal of both theoretical and experimental studies of HER electrocatalysts with special emphasis on the electronic structure, surface (electro)chemistry, and molecular design. It addresses the importance of correlating theoretical calculations and electrochemical measurements toward better understanding of HER electrocatalysis at the atomic level. Fundamental concepts in the computational quantum chemistry and its relation to experimental electrochemistry are also presented along with some featured examples.     

受限于纳米狭缝中的四缔合Lennard-Lones流体的相平衡和界面张力研究

分别用改进的基础测量理论和平均球近似理论表达短程作用和长程作用对四缔合Lennard-Jones流体的过剩自由能的贡献. 在密度函泛理论的框架下, 研究了平均密度等温线, 密度分布, 未缔合分子在平衡汽相和液相中的分布, 相平衡以及平衡时的界面张力等热力学性质. 分析了缔合能量, 流体-固体作用和孔宽对受限于纳米狭缝中的四缔合Lennard-Jones流体相行为的影响.     

Computational studies on electron and proton transfer in phenol‐imidazole‐base triads

The electron and proton transfer in phenol‐imidazole‐base systems (base = NH₂^? or OH^?) were investigated by density‐functional theory calculations. In particular, the role of bridge imidazole on the electron and proton transfer was discussed in comparison with the phenol‐base systems (base = imidazole, H₂O, NH₃, OH^?, and NH₂^?). In the gas phase phenol‐imidazole‐base system, the hydrogen bonding between the phenol and the imidazole is classified as short strong hydrogen bonding, whereas that between the imidazole and the base is a conventional hydrogen bonding. The n value in spⁿ hybridization of the oxygen and carbon atoms of the phenolic CO sigma bond was found to be closely related to the CO bond length. From the potential energy surfaces without and with zero point energy correction, it can be concluded that the separated electron and proton transfer mechanism is suitable for the gas‐phase phenol‐imidazole‐base triads, in which the low‐barrier hydrogen bond is found and the delocalized phenolic proton can move freely in the single‐well potential. For the gas‐phase oxidized systems and all of the triads in water solvent, the homogeneous proton‐coupled electron transfer mechanism prevails. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Toward the complete range separation of non‐hybrid exchange–correlation functional

In this study, we use a very simple scheme to achieve range separation of a total exchange–correlation functional. We have utilized this methodology to combine a short‐range pure density functional theory (DFT) functional with a corresponding long‐range pure DFT, leading to a “Range‐separated eXchange–Correlation” (RXC) scheme. By examining the performance of a range of standard exchange–correlation functionals for prototypical short‐ and long‐range properties, we have chosen B‐LYP as the short‐range functional and PBE‐B95 as the long‐range counterpart. The results of our testing using a more diverse range of data sets show that, for properties that we deem to be short‐range in nature, the performance of this prescribed RXC‐DFT protocol does resemble that of B‐LYP in most cases, and vice versa. Thus, this RXC‐DFT protocol already provides meaningful numerical results. Furthermore, we envisage that the general RXC scheme can be easily implemented in computational chemistry software packages. This study paves a way for further refinement of such a range‐separation technique for the development of better performing DFT procedures. © 2015 Wiley Periodicals, Inc.     

Theoretical Studies on the One‐ and Two‐Photon Absorption Properties of Double‐bis(styryl)benzene Derivatives

Two series of bis(styryl)benzene derivatives (BSBD), namely the single‐BSBD and the double‐BSBD, were investigated. The equilibrium geometries and electronic structures were obtained by using the density functional theory B3LYP and 6‐31G basis set. In succession, the one‐ and two‐photon absorption properties of all the molecules were studied theoretically with a ZINDO‐SOS (sum‐over‐states) method in detail. It can be seen that the double‐BSBDs have larger two‐photon absorption (TPA) cross sections in the visible‐IR range than the corresponding single‐BSBDs, demonstrating that increasing the molecular dimension is a very effective method to enhance the values of the TPA cross sections. On the other hand, it can be also noticed that the values of the TPA cross sections are correlative with the ability of donating (accepting) electrons of the terminal substituent groups R [N(CH₃)₂, CH₃, H and CF₃] in these molecules. That is, the intramolecular charge transfer is also a factor for the enhancement of the TPA efficiency. To sum up, the idea of increasing the molecular dimension to enhance the TPA cross section value is a helpful direction to explore better TPA materials for practical applications. And the double‐BSBD molecules are promising TPA materials for the further investigation from the standpoint of the high transparency and the larger TPA cross sections.     

Electron correlations in Kohn–Sham exchange‐only theory

We provide an interpretation for the “exchange” energy and potential of Kohn–Sham exchange‐only theory, or equivalently that of the optimized potential method (OPM), which shows that in addition to contribution due to the Pauli exclusion principle, there is a kinetic component to these properties. The interpretation is in terms of a conservative field R ^OPM( r ), which is a sum of two fields, one representative of Pauli electron correlations and the other of kinetic effects. The OPM exchange potential is derived via the differential virial theorem to be the work done to move an electron in the field R ^OPM( r ). The OPM exchange energy is then expressed via the integral virial theorem in terms of this field. A similar interpretation for the energy and potential may also be derived directly from the OPM integral equation. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71:473–480, 1999     

A TD‐DFT Study on the Effect of Intermolecular Hydrogen Bonding on the Photophysical Properties of N‐Methyl‐1,8‐naphthalimide

The effect of intermolecular hydrogen bonding on the photophysical properties of N‐methyl‐1,8‐naphthalimide ( 2 ) has been investigated by time‐dependent density functional theory (TD‐DFT) method. The UV and IR spectra of 2 monomer and its hydrogen‐bonded complexes formed with 2,2,2‐trifluoroethanol (TFE) 2 +TFE and 2 +2TFE have been calculated, which confirm the presence of intermolecular hydrogen bonding interactions between the carbonyl groups of the aromatic imide and the hydroxyl group of the polyfluorinated alcohol. The absorption and fluorescence intensities going from 2 monomer via hydrogen‐bonded complex 2 +TFE to 2 +2TFE were found to be gradually enhanced with the wavelength gradually red‐shifted. The enhancements of the fluorescence intensities from 2 monomer to hydrogen‐bonded complexes 2 +TFE and 2 +2TFE were attributed to the decrease of the intersystem crossing (ISC) efficiency from the first excited singlet state S₁ ¹(ππ*) to the second excited triplet state T₂ ³(nπ*), whose energy was increased relative to its ground state due to the intermolecular hydrogen bonding interactions.