The V state of ethylene: valence bond theory takes up the challenge

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	The V state of ethylene: valence bond theory takes up the challenge
	Wu, Wei ; Zhang, Huaiyu ; Braida, Benoit ; Shaik, Sason ; Hiberty, Philippe C. ; Wu W(吴玮)
刊名	http://dx.doi.org/10.1007/s00214-013-1441-x
	2014-01-09
关键词	VERTICAL EXCITATION-ENERGIES COUPLED-CLUSTER CALCULATIONS EXCITED-STATES CONFIGURATION-INTERACTION WAVE-FUNCTIONS DYNAMIC CORRELATION BREATHING ORBITALS BASIS-SETS PI ASTERISK
英文摘要	Natural Science Foundation of China [21120102035, 21273176, 21290193]; Israel Science Foundation (ISF) [1183/13]; The ground state and first singlet excited state of ethylene, so-called N and V states, respectively, are studied by means of modern valence bond methods. It is found that extremely compact wave functions, made of three VB structures for the N state and four structures for the V state, provide an N -> V transition energy of 8.01 eV, in good agreement with experiment (7.88 eV for the N -> V transition energy estimated from experiments). Further improvement to 7.96/7.93 eV is achieved at the variational and diffusion Monte Carlo (MC) levels, respectively, VMC/DMC, using a Jastrow factor coupled with the same compact VB wave function. Furthermore, the measure of the spatial extension of the V state wave function, 19.14 a (0) (2) , is in the range of accepted values obtained by large-scale state-of-the-art molecular orbital-based methods. The sigma response to the fluctuations of the pi electrons in the V state, known to be a crucial feature of the V state, is taken into account using the breathing orbital valence bond method, which allows the VB structures to have different sets of orbitals. Further valence bond calculations in a larger space of configurations, involving explicit participation of the sigma response, with 9 VB structures for the N state and 14 for the V state, confirm the results of the minimal structure set, yielding an N -> V transition energy of 7.97 eV and a spatial extension of 19.16 a (0) (2) for the V state. Both types of valence bond calculations show that the V state of ethylene is not fully ionic as usually assumed, but involving also a symmetry-adapted combination of VB structures each with asymmetric covalent pi bonds. The latter VB structures have cumulated weights of 18-26 % and stabilize the V state by about 0.9 eV. It is further shown that these latter VB structures, rather than the commonly considered zwitterionic ones, are the ones responsible for the spatial extension of the V state, known to be ca. 50 % larger than the V state.
语种	英语
出版者	SPRINGER
内容类型	期刊论文
源URL	[http://dspace.xmu.edu.cn/handle/2288/89416]
专题	化学化工－已发表论文
推荐引用方式 GB/T 7714	Wu, Wei,Zhang, Huaiyu,Braida, Benoit,et al. The V state of ethylene: valence bond theory takes up the challenge[J]. http://dx.doi.org/10.1007/s00214-013-1441-x,2014.
APA	Wu, Wei,Zhang, Huaiyu,Braida, Benoit,Shaik, Sason,Hiberty, Philippe C.,&吴玮.(2014).The V state of ethylene: valence bond theory takes up the challenge.http://dx.doi.org/10.1007/s00214-013-1441-x.
MLA	Wu, Wei,et al."The V state of ethylene: valence bond theory takes up the challenge".http://dx.doi.org/10.1007/s00214-013-1441-x (2014).