梁万珍
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- 姓名:梁万珍
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学术头衔:
博士生导师
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学科领域:
物理化学
- 研究兴趣:
梁万珍教授,1965年出生于四川仪陇;1987年毕业于西南师范大学物理系;1990年获四川大学原子与分子物理所理学硕士学位;后在兰州交通大学任教,主要从事大学普通物理教学,历任助教,讲师和副教授;2001年初博士毕业于香港大学化学系;后在美国加州大学伯克利分校(University of California at Berkeley)化学系和化学工程系做博士后;2003年秋天回国开始任职于中国科技大学化学物理系和合肥微尺度物理科学国家实验室,职称教授。获中国科学院“引进海外杰出人才计划”资助。
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620
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成果数
13
【期刊论文】Localized-Density-Matrix Method and Its Application to Carbon Nanotubes
梁万珍, WanZhen Liang, Satoshi Yokojima, DongHao Zhou, and GuanHua Chen*
J. Phys. Chem. A 2000, 104, 2445-2453,-0001,():
-1年11月30日
The localized-density-matrix method (Yokojima, S.; Chen, G. H. Chem. Phys. Lett. 1998, 292, 379) is employed to simulate the optical responses of very large carbon nanotubes and polyacetylene oligomers containing 10 000 carbon atoms. The Pariser-Parr-Pople Hamiltonian is used to describe the
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【期刊论文】Localized-density-matrix method and nonlinear optical response
梁万珍, WanZhen Liang, Satoshi Yokojima, and GuanHua Chen a)
J. Chem. Phys., Vol. 113, No.4, 22 July 2000,-0001,():
-1年11月30日
The linear scaling localized-density-matrix (LDM) method is generalized to calculate the nonlinear optical responses of large polyacetylene oligomers. The ground state reduced single-electron density matrix is initialized by the divide-and-conquer approach and is obtained subsequently using the LDM method. The third-harmonic generation spectra of large oligomers are calculated. The saturation of off-resonant second hyperpolarizability x (3) (0) has been reinvestigated, and the value of x (3) (0) is found to depend mainly on the optical gap and the number of double bonds.
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【期刊论文】Generalized linear-scaling localized-density-matrix method
梁万珍, WanZhen Liang, Satoshi Yokojima, and GuanHua Chen
J. Chem. Phys., Vol. 110, No.4, 22 January 1999,-0001,():
-1年11月30日
A generalized linear scaling localized-density-matrix (LDM) method is developed to adopt the nonorthonormal basis set and retain full Coulomb differential overlap integrals. To examine its validity, the method is employed to evaluate the absorption spectra of polyacetylene oligomers containing up to 500 carbon atoms. The semiempirical Hamiltonian for the p electrons includes explicitly the overlap integrals among the p orbitals, and is determined from the ab initio Hartree– Fock reduced single-electron density matrix. Implementation of the generalized LDM method at the ab initio molecular orbital calculation level is discussed.
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【期刊论文】Biasing a transition state search to locate multiple reaction pathways
梁万珍, Baron Peters, WanZhen Liang, and Alexis T. Bell Arup Chakraborty a)
J. Chem. Phys., Vol. 118, No.21, 1 June 2003,-0001,():
-1年11月30日
A variety of chemical systems exhibit multiple reaction pathways that adjoin to a common reactant state. In fact, any reaction producing side products or proceeding via a stable intermediate involves a species possessing at least two reaction pathways. Despite improvements in ab initio transition-state search algorithms it remains difficult to detect multiple reaction pathways. Typically, multiple reaction pathways can only be detected by intuitively varying the initial point in the transition-state search trajectory. This reliance on intuition limits the ability to discover new and unexpected chemistry using ab initio methods. This paper proposes a systematic and intuition-free method for biasing a transition-state search to identify multiple reaction pathways originating from a common reactant state. The method allows the successive location of transition states, with each successful search contributing to a cumulative bias potential for the following search. The method is applicable to all psuedo-Newton-Raphson-type transition-state searches. The procedure was tested for a model potential energy surface and for the thermal rearrangement of trans-1,4-dimethylcyclobutene. In the latter case, four reaction pathways were discovered: two exothermic conrotatory ring openings leading to hexadienes, an endothermic methyl migration pathway leading to a carbene, and an exothermic rearrangement leading to 3-methyl-1,4-pentadiene. In accordance with experiment, the calculations predict that the conrotatory pathway leading to trans,trans-2,4-hexadiene is the kinetically dominant pathway. The methodology was also used to compute selectivities for competitive pathways producing trans and cis triflouropentadiene products in the thermal rearrangement of 3-triflouromethyl-cyclobutene. Again, results were in accord with experimental observations.
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梁万珍, WanZhen Liang‡ and Martin Head-Gordon*
J. Phys. Chem. A 2004, 108, 3206-3210,-0001,():
-1年11月30日
Dual basis sets are employed as an economical way to approximate self-consistent field (SCF) calculations, such as Kohn-Sham density functional theory (DFT), in large basis sets. First, an SCF calculation is performed in a small subset of the full set of basis functions. The density matrix in this small basis is used to construct the effective Hamiltonian operator in the large basis, from which a correction for basis set extension is obtained for the energy. This correction is equivalent to a single Roothaan step (diagonalization) in the large basis. We present second order nonlinear equations that permit this step to be obtained without explicit diagonalization. Numerical tests on part of the Gaussian-2 dataset, using the B3LYP density functional, show that large-basis results can be accurately approximated with this procedure, subject to some limitations on the smallness of the small basis. Computational savings are approximately an order of magnitude relative to a self-consistent DFT calculation in the large basis.
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梁万珍, WanZhen Liang, †, ‡, § Alexis T. Bell, *, † Martin Head-Gordon, ‡ and Arup K. Chakraborty†
J. Phys. Chem. B 2004, 108, 4362-4368,-0001,():
-1年11月30日
The reactions of methane with [FeO2]+ and [OFeO)]+ cations exchanged into ZSM-5 have been investigated using density functional theory. Experimental evidence for the latter cation has recently been reported on the basis of EXAFS experiments performed on Fe-ZSM-5 with Fe/Al) 0.17-0.80. Of the two iron-containing species investigated, Z [OFeO] [Z here represents the cation-exchange site in the zeolite] is lower in energy by 7.7 kcal/mol, assuming a spin multiplicity M) 6. The activation energy for the conversion of Z [FeO2] and Z [OFeO] is 10.0kcal/mol. The activation of methane occurs preferentially on Z [OFeO]. Weakly adsorbed methane reacts with Z [OFeO] to produce a weakly bound CH3 free radical. The activation barrier for this process is 15.9kcal/mol. The methyl radical then reacts via a barrierless process to form Z [(OH) Fe (OCH3)]. This product is very stable thermally, but can be converted to adsorbed methanol or formaldehyde via processes exhibiting high activation barriers (39.3kcal/mol in both cases). Hydrolysis of Z [(OH) Fe (OCH3)] to form adsorbed methanol is practically thermoneutral and has an activation barrier of 6.2kcal/mol. The desorption of the adsorbed methanol is endothermic by 18.8kal/mol, but the formation of water from the resulting Z [Fe (OH) 2] has a moderately high activation barrier of 37.9kcal/mol. If N2O is present in the gas phase, the activation barrier for the formation of H2O decreases to 18.1kcal/mol. The results of the present investigation are qualitatively consistent with recent experimental observations.
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【期刊论文】Improved Fermi operator expansion methods for fast electronic structure calculations
梁万珍, WanZhen Liang Chandra Saravanan and Yihan Shao Roi Baer Alexis T. Bell Martin Head-Gordon a)
J. Chem. Phys., Vol. 119, No.8, 22 August 2003,-0001,():
-1年11月30日
Linear scaling algorithms based on Fermi operator expansions (FOE) have been considered significantly slower than other alternative approaches in evaluating the density matrix in Kohn-Sham density functional theory, despite their attractive simplicity. In this work, two new improvements to the FOE method are introduced. First, novel fast summation methods are employed to evaluate a matrix polynomial or Chebyshev matrix polynomial with matrix multiplications totalling roughly twice the square root of the degree of the polynomial. Second, six different representations of the Fermi operators are compared to assess the smallest possible degree of polynomial expansion for a given target precision. The optimal choice appears to be the complementary error function. Together, these advances make the FOE method competitive with the best existing alternatives.
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梁万珍, Joseph E. Subotnik and Yihan Shao WanZhen Liang Martin Head-Gordon
J. Chem. Phys., Vol. 121, No.19, 15 November 2004,-0001,():
-1年11月30日
the Iteractive Subspace#! to compute maxima of homogeneous functions of orthogonal matrices. These algorithms revolve around the mathematical lemma that, given an invertible matrix A, the function f (U)=Tr(AU) has exactly one local (and global) maximum for U special orthogonal [i.e., UUT=1 and det(U)=1]. This is proved in the Appendix. One application of these algorithms is the computation of localized orbitals, including, for example, Boys and Edmiston-Ruedenberg (ER) orbitals. The Boys orbitals are defined as the set of orthonormal orbitals which, for a given vector space of orbitals, maximize the sum of the distances between orbital centers. The ER orbitals maximize total self-interaction energy. The algorithm presented here computes Boys orbitals roughly as fast as the traditional method (Jacobi sweeps), while, for large systems, it finds ER orbitals potentially much more quickly than traditional Jacobi sweeps. In fact, the required time for convergence of our algorithm scales quadratically in the region of a few hundred basis functions (though cubicly asymptotically), while Jacobi sweeps for the ER orbitals traditionally scale as the number of occupied orbitals to the fifth power. As an example of the utility of the method, we provide below the ER orbitals of nitrated and nitrosated benzene, and we discuss the chemical implications.
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梁万珍, WanZhen Liang a) and Martin Head-Gordon b)
J. Chem. Phys., Vol. 120, No.22, 8 June 2004,-0001,():
-1年11月30日
A new formulation of the diagonalization step in self-consistent-field (SCF) electronic structure calculations is presented. It exactly replaces the diagonalization of the effective Hamiltonian with the solution of a set of second order nonlinear equations. The density matrix and/or the new set of occupied orbitals can be directly obtained from the resulting solution. This formulation may offer interesting possibilities for new approaches to efficient SCF calculations. The working equations can be derived either from energy minimization with respect to a Cayley-type parametrization of a unitary matrix, or from a similarity transformation approach.
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【期刊论文】Absorption spectra and chirality of single-walled 4
梁万珍, WanZhen Liang and GuanHua Chen a) Zhaoming Li and Zi-Kang Tang
Appl. Phys. Lett., Vol. 80, No.18, 6 May 2002,-0001,():
-1年11月30日
Absorption spectrum of recently discovered single-walled 4
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