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Lu T.,University of Science and Technology of China | Lu T.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | Chen F.,University of Science and Technology of China | Chen F.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials
Journal of Molecular Graphics and Modelling | Year: 2012

Quantitative analysis of molecular surface is a valuable technique for analyzing non-covalent interaction, studying molecular recognition mode, predicting reactive site and reactivity. An efficient way to realize the analysis was first proposed by Bulat et al. (J. Mol. Model., 16, 1679), in which Marching Tetrahedra (MT) approach commonly used in computer graphics is employed to generate vertices on molecular surface. However, it has been found that the computations of the electrostatic potential in the MT vertices are very expensive and some artificial surface extremes will be presented due to the uneven distribution of MT vertices. In this article, we propose a simple and reliable method to eliminate these unreasonably distributed surface vertices generated in the original MT. This treatment can save more than 60% of total analysis time of electrostatic potential, yet the loss in accuracy is almost negligible. The artificial surface extremes are also largely avoided as a byproduct of this algorithm. In addition, the bisection iteration procedure has been exploited to improve accuracy of linear interpolation in MT. The most appropriate grid spacing for surface analysis has also been investigated. 0.25 and 0.20 bohr are recommended to be used for surface analysis of electrostatic potential and average local ionization energy, respectively. © 2012 Elsevier Inc.


Lu T.,University of Science and Technology of China | Lu T.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | Chen F.,University of Science and Technology of China | Chen F.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials
Journal of Molecular Modeling | Year: 2013

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 (H 2)2, (N2)2, and (H 2)(N2) are investigated by state-of-the-art quantum chemistry calculations and energy decomposition analysis. It is shown that their configuration preferences are essentially controlled by the electrostatic component rather than the dispersion effect though the monomers have zero dipole moment. These configuration preferences can also be fairly well and conveniently interpreted by visually examining the electrostatic potential map. © 2013 Springer-Verlag Berlin Heidelberg.


Chen F.,University of Science and Technology of China | Chen F.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | Fan Z.,University of Science and Technology of China | Fan Z.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials
Journal of Computational Chemistry | Year: 2014

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 two types of supermolecules composed of H2 and BH monomers. Spectroscopic constants of F2(X1Σg+),Cl2(X1Σg+),C2-(X2Σg+),B2(X3Σg-), and C2+(X4Σg-) as well as the ground state energies of H2O, NH2, and CH2 at three bond lengths have been calculated with the second multireference perturbation theory. The dissociation behaviors of CH4 and HF have also been investigated. Comparisons with other approximate theoretical models as well as the experimental data have been carried out to show their relative performances. © 2013 Wiley Periodicals, Inc.


Chen F.W.,University of Science and Technology of China | Chen F.W.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | Lu T.,University of Science and Technology of China | Lu T.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | And 2 more authors.
Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica | Year: 2015

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 adsorption at equilibrium. No hypothetical dividing surface is needed in this derivation. The new equation is quite different from the Gibbs adsorption equation. We also performed molecular dynamic simulations of aqueous sodium chloride solutions. The simulated results are in good agreement with our theoretical predictions. © 2015, Editorial office of Acta Physico-Chimica Sinica.


Zhu Q.-Q.,University of Science and Technology Beijing | Zhu Q.-Q.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | Zhou H.-L.,University of Science and Technology Beijing | Zhou H.-L.,Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials | And 6 more authors.
Beijing Keji Daxue Xuebao/Journal of University of Science and Technology Beijing | Year: 2014

Carbon samples were prepared from cellulose by carbonization under the nitrogen atmosphere and water steam activation. Their structure and specific surface area during carbonation and activation processes were studied by thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, and nitrogen adsorption at low temperature. The results show that groups in the cellulose molecular structure like C-OH, C-O-C and C-H are mostly pyrolyzed completely between 280-380℃. A few fragments or surface groups produced during pyrolysis decompose continuously above 380℃. Meanwhile, carbon atoms rearrange within the solid sample and form graphite crystallites. Carbonization temperature exerts a crucial influence on the microcrystalline carbon structure and pore structure. With the rise of carbonation temperature, the size of graphite crystallites increases and the pore structure develops, but the specific surface area of the carbon prepared first increases and then decreases, reaching maximum at 600℃. Carbonization time has less significant influence on the structures. With increasing activation time, non-crystalline carbon is oxidized, the specific surface area and total pore volume of the carbon sample increase simultaneously. However, a longer activation time causes that the original crystalline carbon structure is destroyed, the specific surface area and total pore volume of the carbon sample decrease. The porosity is mostly abundant when non-crystalline carbon is fully oxidized and the original crystalline carbon structure is not destroyed. ©, 2014, University of Science and Technology Beijing. All right reserved.

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