Browsing by Author "Li, Bo"

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A Density Functional Theory Study on Nonlinear Optical Properties of Double Cage Excess Electron Compounds: Theoretically Design M[Cu(Ag)@(NH3)(n)](M = Be, Mg and Ca; n=1-3)
(2019-04-05)
Liang, Yan Ying
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Li, Bo
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Xu, Xuan
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Gu, Feng Long
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Zhu, Chaoyuan
In this work, we investigated the nonlinear optical (NLO) properties of excess electron electride molecules of M[Cu(Ag)@(NH3)(n)](M = Be, Mg and Ca; n = 1-3) using density functional theory (DFT). This electride molecules consist of an alkaline-earth (Be, Mg and Ca) together with transition metal (Cu and Ag) doped in NH3 cluster. The natural population analysis of charge and their highest occupied molecular orbital suggests that the M[Cu(Ag)@(NH3)(n)] compound has excess electron like alkaline-earth metal form double cage electrides molecules, which exhibit a large static first hyperpolarizability (beta(e)(0)) (electron contribution part) and one of which owns a peak value of beta(e)(0) 216,938 (a.u.) for Be [Ag@(NH3)(2)] and vibrational harmonic first hyperpolarizability [(beta(nr)(zzz)) (nuclear contribution part) values and the ratio of beta(nr)(zzz)/beta(e)(zzz'), namely, eta values from 0.02 for Be[Ag@(NH3)] to 0.757 for Mg [Ag@(NH3)(3)]. The electron density contribution in different regions on beta(e)(zzz) values mainly come from alkaline-earth and transition metal atoms by first hyperpolarizability density analysis, and also explains the reason why beta(e)(zzz) values are positive and negative. Moreover, the frequency-dependent values ss(-2 omega,omega,omega) are also estimated to make a comparison with experimental measures. (c) 2018 Wiley Periodicals, Inc.
A nonlinear optical switch induced by an external electric field: inorganic alkaline-earth alkalide
(2019-05-28)
Li, Bo
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Peng, Daoling
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Gu, Feng Long
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Zhu, Chaoyuan
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應用化學系分子科學碩博班
Exploring a new type of nonlinear optical switch molecule with excess electron character is extremely important for promoting the application of excess electron compounds in the nonlinear optical (NLO) field. Here, we report external electric field (EEF) induced second-order NLO switch molecules of inorganic alkaline-earth alkalides, M(NH3) 6Na2 (M = Mg or Ca). The centrosymmetric structure of M(NH3) 6Na2 is destroyed in the presence of an EEF, and then a long-range charge transfer process occurs. It has been found that excess electrons are gradually transferred from one Na atom to the other Na atom through the inorganic metal cluster M(NH3) 6. Finally, the excess electrons are completely located on one of the two Na atoms. In particular, the electronic contribution of the static first hyperpolarizability (b e 0) for M(NH3) 6Na2 exhibits a large significant difference when the EEF is switched on. The b e 0 value of M(NH3) 6Na2 is 0 when EEF = 0, while the peak b e 0 values are 5.95 106 (a. u.) for Mg(NH3) 6Na2 (EEF = 58 10 4 (a. u.)) and 1.83 107 (a. u.) for Ca(NH3) 6Na2 (EEF = 53 10 4 (a. u.)). This work demonstrates that the compounds M(NH3) 6Na2 can serve as potential candidates for NLO switches.
Facially Polarized Molecule for Alkalides and Superalkalides with Considerable Nonlinear Optical Response
(2018-12-06)
Li, Bo
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Peng, Daoling
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Gu, Feng Long
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Zhu, Chaoyuan
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應用化學系
In this work, alkali M (Li and K) and superalkali M ' O-3 (M '=Li and Na) combined with facially polarized molecule, all-cis 1,2,3,4,5,6-Hexafluorocyclohexane (L, C6H6F6), were utilized to design novel alkalides L-M-L-M ' and superalkalides L-M-L-M ' O-3, respectively. Computational results show that alkalides L-M-L-M ' and superalkalides L-M-L-M ' O-3 have high thermodynamic stability, and the superalkalides L-M-L-M ' O-3 are more stable than the alkalides L-M-L-M '. Importantly, they also possess remarkable NLO responses, the electronic contribution of the static first hyperpolarizability (beta(e)(0)) has upped to 3.42x10(6) (a.u.) for L-K-L-Li3O. In particularly, the number of ligand L considerably impacts on beta(e)(0) value, namely, the beta(e)(0) value of Li-L-Li3O can be improved two orders of magnitude by adding additional ligand L, 1.31x10(6) (a.u.)(L-Li-L-Li3O) > 7.76x10(4) (a.u.)(Li-L-Li3O). We hope this work can attract researchers to design and synthesize novel excess electron compounds with high performance NLO materials.
Insight into the Expanded Mislinked Porphyrins with High Second Order Nonlinear Optical Response
(2020-02-06)
Li, Bo
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Sathishkumar, Palanivel
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Gu, Feng Long
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Zhu, Chaoyuan
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應用化學系
Materials with outstanding nonlinear optical (NLO) response exhibit excellent prospects in electrooptic devices. Thus, it is essential to find a high-performance NLO material to meet the growing demand for high-speed data transmission. In this study, theoretical investigations on the second order NLO properties of the novel expanded mislinked thia-norhexaphyrin, sulfur-free pentaphyrin, and their substituted derivatives were performed using density functional theory. Theoretical calculations display that the approximate planar structures of sulfur-free pentaphyrin embedded with two five-membered rings exhibits a remarkable NLO response and holds large dipolar contribution (Phi(J=1) = 63.5%) to the first hyperpolarizability among four parent expanded mislinked porphyrins. The static first hyperpolarizability values of these expanded porphyrins were found to range from 3490 to 14 229 au. In addition, the second order NLO response of these porphyrins has greatly improved except for minority electron-releasing- and electron-withdrawing-group substituted cases, and the static first hyperpolarizability value has increased to 47 950 au after installing the donor and acceptor groups. Unambiguous evidence reveals that expanded mislinked porphyrin can serve as a potential candidate for NLO materials.
Mitigate the Obstructing Effect of Vehicles on the Propagation of VANETs Safety-Related Information
(2018-07-01)
Huang, Rui
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Wu, Jing
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Long, Chengnian
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Zhu, Yanmin
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Li, Bo
As physical obstacles, vehicles have significant impacts on the efficient propagations of safety-related information in vehicular ad hoc networks (VANETs) by frequently obstructing the LOS links between transmitters and receivers. Obstructing effect will diminish the effective coverage of safety-related information and incur severe impact on road safety. However, this impact has not been addressed effectively. In this paper, we first present the definition of broadcast efficiency as the metric for quantizing the obstructing effect. We investigate the optimization issue for mitigating the impact of obstructing effect on the propagation of safety-related information and propose a graph theory based optimization algorithm. For a distributed implementation of this optimization in VANETs, we further propose the maximum broadcast efficiency relaying (MBER) algorithm. MBER maximizes the effective coverage of information, meanwhile, meets delay and reliability constraints by incorporating broadcast efficiency and propagation distance in relay contention. Simulation results demonstrate that MBER promotes the effective coverage of safety-related information in VANETs with varying vehicular distribution.
Remarkable nonlinear optical response of excess electron compounds: theoretically designed alkali-doped aziridine M-(C2NH5)(n)
(2017-09-21)
Li, Bo
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Xu, Chao
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Xu, Xuan
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Zhu, Chaoyuan
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Gu, Feng Long
Theoretically designed alkali-doped aziridine M-(C2NH5)(n) (M = Li, Na and K; n = 1, 2, 3, and 4) are investigated by density functional theory (DFT) and time-dependent TD-DFT. The interaction energies at optimized electronic structures indicate that alkali-doped aziridine are quite stable. The natural population analysis of charges on alkali atoms show that all positive and electronic transitions to LUMO orbitals are large, so that the designed compounds not only have electride features, but also have large flexible ligands. This leads to a high-performance nonlinear optical response (NLO) and this remarkable NLO response mainly comes from alkali atoms. By calculating the first hyperpolarizabilities for M-(C2NH5)(4) with M@ Calix[4] pyrrole for comparison, we demonstrate that enhancements of the NLO response of M-(C2NH5)(4) are 10 to 100 times larger than those of M@ Calix[ 4] pyrrole, and in particular, the largest first hyperpolarizability values of Na-(C2NH5)(4) is up to 3.4 x 10(6) (a. u.).
SPRCA: Distributed Multisource Information Propagation in Multichannel VANETs
(2017-12-01)
Huang, Rui
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Wu, Jing
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Long, Chengnian
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Zhu, Yanmin
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Li, Bo
Information dissemination in VANETs mainly focuses on, e.g., the propagation of cooperative awareness messages and decentralized environmental notification messages on the control channel. As vehicles advance toward higher automation levels, VANETs should support more complex traffic services, which generates the demand for the propagation of Internet Protocol (IP)-based information and service data in multichannel environment as specified by IEEE Standard for Wireless Access in Vehicular Environments (WAVE). Multisource propagation in the multichannel environments will incur multisource relay confliction (MRC) which leads to higher latency and lower information propagation speed (IPS). However, the problem of how to mitigate the impact of MRC and maintain high IPS has not been studied sufficiently. In this paper, we propose success probability based relay contention algorithm (SPRCA) for mitigating the impact of MRC under WAVE channel environments. SPRCA presents a vital metric, success probability, for each vehicle to determine whether to join the relay candidate set of certain source and execute relay contention algorithm. SPRCA explores both real time location information of vehicles and stochastic properties of vehicular distribution. We construct a theoretical model for analyzing the performance of SPRCA with a stochastic geometry-based approach and derive the properties of the performance of SPRCA. We further demonstrate the network performance and the practicality in dynamic VANETs of SPRCA through simulations with realistic traffic flow data.