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1.
Celestino Angeli Mariachiara Pastore Renzo Cimiraglia 《Theoretical chemistry accounts》2007,117(5-6):743-754
The n-electron valence state perturbation theory (NEVPT) is a form of multireference perturbation theory which is based on a zero
order reference wavefunction of CAS-CI type (complete active space configuration interaction) and which is characterized by
the utilization of correction functions (zero order wavefunctions external to the CAS) of multireference nature, obtained
through the diagonalization of a suitable two-electron model Hamiltonian (Dyall’s Hamiltonian) in some well defined determinant
spaces. A review of the NEVPT approach is presented, starting from the original second order state-specific formulation, going
through the quasidegenerate multi-state extension and arriving at the recent implementations of the third order in the energy
and of the internally contracted configuration interaction. The chief properties of NEVPT—size consistence and absence of
intruder states—are analyzed. Finally, an application concerning the calculation of the vertical spectrum of the biologically
important free base porphin molecule, is presented. 相似文献
2.
Celestino Angeli Renzo Cimiraglia Maurizio Persico Alessandro Toniolo 《Theoretical chemistry accounts》1997,98(1):57-63
We discuss the “three class” approximation to full multireference perturbation CI, which greatly reduces the computational
effort by restricting the summation of diagrams to determinants belonging to a subspace of the zero-order space. In the framework
of the CIPSI algorithm, we propose a new extrapolation procedure allowing recovery of the full “two class” results. The new
procedure is applied to complete active spaces (CAS) and to individually selected zero-order spaces. Comparison with a full
two class calculation on a CAS shows a reduction of computer time of one or two orders of magnitude in the tests presented
here, with an accuracy in the order of 0.1 kcal/mol. Our procedure can thus compete with the CASPT2 algorithm, specifically
conceived to deal with CAS. In the case of selected zero-order spaces, the speed-up is less dramatic but the method still
retains its advantages.
Received: 12 June 1997 / Accepted: 31 July 1997 相似文献
3.
Mariachiara Pastore Celestino Angeli Renzo Cimiraglia 《Theoretical chemistry accounts》2007,118(1):35-46
The vertical electronic spectrum of the thiophene molecule is investigated by means of second and third order multireference
perturbation theory (NEVPT). Single-state and quasi-degenerate NEVPT calculations of more than 25 singlet excited states have
been performed. The study is addressed to the theoretical characterization of the four lowest-energy valence states, as well as the 3s, 3p and 3d Rydberg states. In addition, the excitation energies of two and valence states are also reported. For almost all the excited states, coupled cluster calculations (CCSD and CCSDR(3)) have
been also carried out, using the same geometry and basis set used for the NEVPT ones, in order to make the comparison between
the results of the two methods meaningful. A remarkable accordance between the NEVPT and CC excitation energies is found.
The present results, over all, confirm the experimental assignments but, above all, represent an important contribution to
the assignments of some low-energy states, valence and Rydberg, for which a firm interpretation is not available in the literature. 相似文献
4.
We present in this paper a modification of the selection procedure, within the CIPSI algorithm, specifically intended for
the calculation of one-electron properties. In this new procedure the determinants are selected following their contribution
to a certain one-electron property. As test cases we report the calculation of the electric dipole of carbon monoxide and
of the hyperfine coupling constants of the CH3 radical.
Received: 20 August 2000 / Accepted: 2 October 2000 / Published online: 21 December 2000 相似文献
5.
Robert F. Hudson 《Angewandte Chemie (International ed. in English)》1973,12(1):36-56
The perturbation method of treating chemical reactions is discussed in a simple manner, by invoking the general hypothesis that the initial perturbation determines the course of a reaction. This approach is used to develop a general theory, as an alternative to the transition state theory. Such apparently diverse concepts as the symmetry rules for cyclic processes, and hard and soft acids and bases can be derived by this treatment, which is applied to radical reactions and aliphatic and aromatic substitution. 相似文献
6.
采用由H2、He 和LiH分别组成的三个超分子系列, 从数值的角度研究了多参考态微扰理论和单双重激发的多参考态组态相互作用(MRSDCI)的大小一致性. 首先在模型空间中进行一个小的完全组态相互作用计算, 然后进行多参考态微扰计算. 数值结果显示, 对这三个模型体系, 我们以前提出的多参考态二级微扰公式是完全大小一致的. 和MRSDCI结果比较, 我们也对它的计算精度进行了讨论. 另外, 还对两组多参考态微扰理论的二级和三级计算结果以及MRSDCI的计算结果的大小一致性误差进行了研究和比较. 相似文献
7.
8.
Matthias Schüler Thomas Kovar Hans Lischka Ron Shepard Robert J. Harrison 《Theoretical chemistry accounts》1993,84(6):489-509
Summary In this work a parallel implementation of the COLUMBUS MRSDCI program system is presented. A coarse grain parallelization approach using message passing via the portable toolkit TCGMSG is used. The program is very well portable and runs on shared memory machines like the Cray Y-MP, Alliant FX/2800 or Convex C2 and on distributed memory machines like the iPSC/860. Further implementations on a network of workstations and on the Intel Touchstone Delta are in progress. Overall, results are quite satisfactory considering the complexity and the prodigious requirements, especially the I/O bandwidth, of MRCI programs in general. For our largest test case we obtain a speedup of a factor of 7.2 on an eight processor Cray Y-MP for that section of the program (hamiltonian matrix times trial vector product) which has been parallelized. The speedup for one complete diagonalization iteration amounts to 5.9. An absolute speed close to 1 GFLOPS is found. Results for the iPSC/860 show that ordinary disk I/O is certainly not sufficient in order to guarantee a satisfactory performance. As a solution for that problem, the implementation of a fully asynchronous distributed-memory model for certain data files is in preparation.
On leave from: Bereich Informatik, Universität Leipzig, Augustusplatz 10/11, O-7010 Leipzig, Germany 相似文献
9.
Celestino Angeli Renzo Cimiraglia Maurizio Persico 《Theoretical chemistry accounts》1998,100(5-6):324-328
Within the frame of multireference perturbation configuration interaction we have developed a fast algorithm, based on diagrammatic
techniques, for the calculation of the first-order correction to the one-particle density matrix. As an example of an application
we have chosen the evaluation of the dipole moment of the CO molecule, where utilization of the first-order density is shown
to corroborate the variational calculation.
Received: 4 August 1998 / Accepted: 21 September 1998 / Published online: 16 November 1998 相似文献
10.
采用二阶多参考微扰理论计算了F, Cl, OH, SH, CN, CH2和NH2的电子亲和势.另外,还考察了基函数和完全活性空间大小对电子亲和势精度的影响.通过和CASSCF, CASPT2, CCSD, CCSD(T), B3LYP, X3LYP, M06, HCTH, TPSS, B97D3, mPW2PLYP和B2PLYP的计算结果比较发现,针对目前所用的基函数,二阶多参考态微扰理论的总体计算效果是最好的. 相似文献
11.
Asymptotic Functional Form Preservation Method for the Perturbation Theory: Application to Anharmonic Oscillators 下载免费PDF全文
The asymptotic functional form preservation method is developed for the perturbation theory to obtain the energy eigenvalues of anharmonic oscillators. The conventional energy perturbative series expansion for the anharmonic oscillator is strongly divergent even if the anharmonicity is small. Employing a transformation containing an unphysical parameter, we analytically continue this series expansion into a new series expansion applicable to all the range of the perturbation parameter. The unphysical parameter is determined by the principle of minimal sensitivity. This new series expansion is reduced to the conventional energy perturbative series expansion for small anharmonicity, and it preserves the correct asymptotic functional form when the perturbation parameter tends to infinity. Then, we use the full‐range energy series expansion to calculate the energy eigenvalues of the anharmonic oscillator. In addition to excellent energy eigenvalues obtained for the oscillator with small and strong anharmonicity, accurate energy eigenvalues can be obtained using the full‐range energy series expansion when the perturbation parameter tends to infinity. 相似文献
12.
从硬球微扰理论推导马丁-侯状态方程 总被引:4,自引:0,他引:4
从Barher-Henderson的硬球微扰理论出发,运用幂级数形式的径向分布函数和分段的势能函数导出马丁-侯状态方程,推导过程中导出了一种理论式,计算P-V-T性质的精确度与马丁-侯原式相当,理论式的常数与分子微观参数有确定的函数关系。 相似文献
13.
传统单参考电子相关方法已经发展成熟,但很多时候无法正确描述共价键解离、双(多)自由基和激发态等电子之间相关性非常强的体系。近年来发展的多参考微扰理论和多参考耦合簇理论以多个行列式的线性组合为参考波函数,采用不同的方式有效考虑电子之间的动态相关,对强关联体系的描述取得了显著的改进。但根据理论出发点和精度要求的不同发展出了许多多参考理论,仍无一个公认的、令人满意的方案。本文将结合与常见电子相关方法在理论框架和计算精度上的比较,详细阐述块相关理论的基本原理,并介绍基于块相关的"另类"多参考电子相关方法。最后本文还简单展望了多参考电子相关方法今后的发展趋势。 相似文献
14.
Recently, we demonstrated that the reaction of certain 2-phenylbicyclo-[1.1.0]butanes with rhoium dicrbonyl chloride dimer produced dihydroazulenes, which, on oxidation, were converted to azulenes.3. The utility of this process for the preparation of azulene derivatives was limited by the availability of the phenyl substituted bicyclo[1.1.0]butanes. Although the C-H insertion reaction, developed by Moore and coworkers4 for the preparation of 2-phenylbicyelo[1.1.0]butanes from dibromocyclopropanes, works very well, the required absence of cyclopropyl hydrogans, and the problems inherent in the preparation of the hexasubstituted dibromocyclopropane intermediates made the overall synthesis of azulenes by this route rather tedious. We now wish to report a simplified approach to the synthesis of azulenes whis has as one of the critical steps, the transition metal complex promoted rearrangement of a 2-phenylbicyclo[1.1.0]butane. 相似文献
15.
两种哈密顿量划分的单参考态微扰展开式的大小一致性研究 总被引:1,自引:0,他引:1
利用一个含N个氢分子的超分子模型, 从解析的角度仔细地分析了相应于两种哈密顿量划分方式的单参考态微扰展开式前四级能量的大小一致性. 对于Epstein-Nesbet划分, 微扰展开式是大小一致的. 而对于另一种划分(Chen, F; Davidson, E. R.; Iwata, S. Int. J. Quantum Chem., 2002, 86: 256, 见公式(24)的讨论), 其展开式大小不一致. 但将它的分母作泰勒展开, 经过重新整理, 将那些大小不一致的项消去后, 得到的新微扰展开式是逐项大小一致的. 相似文献
16.
张秉坚 《高等学校化学学报》1995,16(9):1440-1444
提出在Barker与Henderson的压缩性近似推导中,相邻壳层之间的分子数应该相关,导出了相关系数和改进的二级微扰项,提高了高级微扰项在较高密度区的准确性。对二级以上的高级微扰项采用Barker与Henderson的近似方法,得到一个简单的微扰理论表达式,以硬球势为参考势,方阱势为微扰势,用一新的级数形式的径向分布函数导出了自由能、内能、比热、压缩因子的级数表达式。其四项截断式的计算结果与MC、MD计算机模拟值符合较好。 相似文献
17.
The diagrammatic Rayleigh-Schr?dinger perturbation theory for the interaction of two closed-shell systems is developed up
to the third order of pertur-bation using orthogonalized orbitals. The interaction energy is expressed by the Rayleigh-Schr?dinger
perturbation expansion. A simple approach for the estimation of basis set superposition error is introduced. The preliminary
calculations of the intermolecular interactions for the He dimer within the augmented cc-pVTZ basis set are compared with
the supermolecular approach, perturbation calculation in biorthogonal basis sets and symmetry adapted perturbation theory
results.
Received: 17 December 1996 / Accepted: 5 November 1997 相似文献
18.
19.
ZHANG Bing-jian 《高等学校化学研究》2000,16(1):49-56
IntroductionIn the mid 1950's, an empirical equation of state was proposed by Martin and HouLI] abbreviated to the M--H equation. It is a more accurate equation of state applicable to real gasesincluding polar compounds, such as ammonia and water over a wide range of density and temperature. In 1981, the M--H equation was extended further to liquid domain by Hou et al. [2),and later, it was used to calculate the vapor--liquid equilibrium, liquid--liquid equilibrium andother thermodynamic p… 相似文献
20.
P. Reinhardt 《Theoretical chemistry accounts》2006,116(4-5):655-663
The dressed diagonal approximation to the self-consistent – size consistent CI, corrected for off-diagonal Fock matrix elements in localized orbitals is developed and applied to the ammoniac dimer system. A quite correct correlation energy can be obtained for this system, with a significantly reduced dependence of the results on the choice of the localization procedure. When calculating an interaction energy, the choice of the monomer orbitals and the application of the Boys–Bernardi counterpoise procedure shows in this case an unusual behavior: the correlation energy does not increase with the size of the atomic basis sets. Nevertheless a reasonable potential curve can be obtained. 相似文献