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51.
Summary The invariance of the configuration interaction (CI) energy with respect to orbital rotation is considered. The inclusion of all spin couplings versus only those from the first-order interacting space is considered. A definition for the analog of a second-order CI calculation when inactive electrons are present is proposed. 相似文献
52.
Optimization of virtual orbitals in the framework of a multiconfiguration spin-coupled wave function
Nick J. Clarke Mario Raimondi Maurizio Sironi Joseph Gerratt David L. Cooper 《Theoretical chemistry accounts》1998,99(1):8-17
A new method is introduced for the optimization of nonorthogonal virtual orbitals for use in general multiconfiguration spin-coupled wave functions. The use of a number of highly effective approximations greatly reduces the computational effort
involved, the most important being the use of a second-order perturbation expression for the energy and an approximate expression
for the elements of the Hessian. As a result, the overall scheme scales very favourably with respect to the numbers of active
electrons and of basis functions, making it suitable for the accurate study of large systems. Benchmark calculations are presented
for the dissociation of LiH(X1Σ+) and Li2(X1Σ+
g
) using a highly compact four-configuration wave function. Standard spin-coupled valence bond expansions in the same virtual
space are required to be significantly larger before equivalent results are obtained. The results are shown to compare very
favourably with full valence complete active space self-consistent field calculations using an identical basis, and binding
energies are within 4% of the values obtained from full configuration interaction calculations in the same basis set.
Received: 10 June 1997 / Accepted: 7 October 1997 相似文献
53.
Computer aided drug identification in toxicological analysis by means of EI and CI mass spectrometry
U. Rapp A. Zune W. Ehrenthal und K. Pfleger 《Fresenius' Journal of Analytical Chemistry》1976,279(2):133
Ohne Zusammenfassung
Computer aided drug identification in toxicological analysis by means of EI and CI mass spectrometry相似文献
54.
在AM1方法优化的几何结构基础上,用INDO/CI-SOS方法深入探讨亚酞菁(C24H12B1Cl1N6)的硝基取代对体系的电子光谱和二阶非线性光学性质的影响.结果表明,吸电子取代基和取代基的共轭链的增长对亚酞菁的分子结构和电子光谱的最大吸收峰影响很小,但对非线性光学性质都有较大影响,随着共轭链的增长,二阶非线性光学系数大幅度增强.未被取代的亚酞菁的β0计算值与实验值十分相符,分别为-0.73×10-28和-0.70×10-28esu,共轭链最长的硝基取代化合物β0值增大到-1.47×10-28esu,增加约近1倍. 相似文献
55.
56.
57.
Riadh Dardouri Héla Habli Brahim Oujia Florent Xavier Gadéa 《Journal of computational chemistry》2013,34(24):2091-2099
For all states dissociating below the ionic limit Li? Rb+, we perform a diabatic study for 1Σ+ electronic states dissociating into Rb (5s, 5p, 4d, 6s, 6p, 5d, 7s, 4f) + Li (2s, 2p, 3s). Furthermore, we present the diabatic results for the 1–11 3σ, 1–8 1,3Π, and 1–4 1,3Δ states. The present calculations on the RbLi molecule are complementary to previous theoretical work on this system, including recently observed electronic states that had not been calculated previously. The calculations rely on ab‐initio pseudopotential, core polarization potential operators for the core‐valence correlation and full valence configuration interaction approaches, combined to an efficient diabatization procedure. For the low‐lying states, diabatic potentials and permanent dipole moments are analyzed, revealing the strong imprint of the ionic state in the 1Σ+ adiabatic states. The transition dipole moment is used to evaluate the radiative lifetimes of the vibrational levels trapped in the 2 1Σ+ excited states for the first time. In addition to the bound–bound contribution, the bound–free term has been evaluated using the Franck–Condon approximation and also exactly added to the total radiative lifetime. © 2013 Wiley Periodicals, Inc. 相似文献
58.
59.
A new selected-configuration interaction method is proposed, based on the use of local orbitals. A corresponding code has been written, which is devoted to CI calculations of rather large systems (about 50-100 carbon-like atoms). Taking advantage of the locality, and then of the fact that interactions vanish when the distance is large, the dimension of the CI space is largely reduced. The determinants that would be created by long range excitations are expected to have a small weight in the wave function and are therefore eliminated. This selected excitation CI space is particularly suited for large molecules. It is tested on large polyene chains and on a transition metal complex. For large enough systems, the CPU time saving is important and, what is more noticeable, calculations that were impossible to perform without selection are feasible in this approach. 相似文献
60.
用全相对论多组态自洽场方法,计算了HgII离子的5d10nl、5d96s2、5d9nsnp、5d96p2和5d86s26p等组态的3840个精细结构能级和辐射寿命以及各种跃迁参数.能级的计算值和实验值符合得较好.同时,我们还发现了一些长寿命亚稳态能级. 相似文献