2021 News


 2021/06/03

 

 

Congratulations to Yuanheng Wang for his new paper has been published in J. Chem. Phys.!
 
In this work, we propose a new method to calculate molecular nonradiative electronic relaxation rates based on the numerically exact timedependent density matrix renormalization group theory. This method could go beyond the existing frameworks under the harmonic approximation (HA) of the potential energy surface (PES) so that the anharmonic effect could be considered, which is of vital importance when the electronic energy gap is much larger than the vibrational frequency. We calculate the internal conversion (IC) rates in a two-mode model with Morse potential to investigate the validity of HA. We find that HA is unsatisfactory unless only the lowest several vibrational states of the lower electronic state are involved in the transition process when the adiabatic excitation energy is relatively low. As the excitation energy increases, HA first underestimates and then overestimates the IC rates when the excited state PES shifts toward the dissociative side of the ground state PES. On the contrary, HA slightly overestimates the IC rates when the excited state PES shifts toward the repulsive side. In both cases, a higher temperature enlarges the error of HA. As a real example to demonstrate the effectiveness and scalability of the method, we calculate the IC rates of azulene from S1 to S0 on the ab initio anharmonic PES approximated by the one-mode representation. The calculated IC rates of azulene under HA are consistent with the analytically exact results. The rates on the anharmonic PES are 30%–40% higher than the rates under HA.
 

2021/05/24

 

Congratulations to Lu Wang !
 
Congratulations to Lu Wang for completing her PhD Dissertation Defense !

 2021/05/24

 

Congratulations to Guodong Wang !
 
Congratulations to Guodong Wang for completing his PhD Dissertation Defense !

 2021/05/24

 

Congratulations to Sheng Huang !
 
Congratulations to Sheng Huang for completing his Master Dissertation Defense !

2021/03/28

Congratulations to Yufei Ge on his published paper in Appl. Phys. Lett.!

The Seebeck effect or thermopower relates the temperature gradient to the electric voltage drop. Seebeck coefficient a measures the transport entropy, which could either linearly increase with temperature T like metallic conducting or decrease as 1/T like semiconducting behavior. It could become more complicated in the temperature dependence for a number of disordered systems but still in a monotonic way. However, several recent experiments reported the “abnormal” non-monotonic temperature dependence of the Seebeck coefficient in doped conducting polymers, for instance, first increasing and then decreasing. Through a one-dimensional tight-binding model coupled with the Boltzmann transport equation, we investigate theoretically the doping effect for the Seebeck coefficient. We find that the abnormal behavior comes from multi bands’ contribution and a two-band model (conduction or valence band plus a narrow polaronic band) can address such an abnormal Seebeck effect, namely, if there exists (i) a small bandgap accessible for thermal activation between the two bands; and (ii) a large difference in the bandwidth between the polaronic band and the conduction band (or valence band), then the Seebeck coefficient increases with temperature first, then levels off, and finally drops down.

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2021/03/18

Congratulations to Shiyun Lin on her published paper in J. Phys. Chem. Lett.!

The two-coordinate carbene−metal−amide complexes have attracted a great deal of attention due to their remarkable thermally activated delayed fluorescence (TADF) properties, giving them promise in organic light-emitting diode application. To reveal the inherent mechanism, we take CAAC−Cu(I)−Cz and CAAC−Au(I)−Cz as examples to investigate the photophysical properties in solution and solid phases by combining quantum mechanics/molecular mechanics approaches for the electronic structure and the thermal vibration correlation function formalism for the excited-state decay rates. We found that both intersystem crossing (ISC) and its reverse (rISC) are enhanced by 2−4 orders of magnitude upon aggregation, leading to highly efficient TADF, because (i) the metal proportion in the frontier molecular orbitals increases, leading to an enhanced spin−orbit coupling strength between S1 and T1, and (ii) the reaction barriers for ISC and rISC are much lower in solution than in aggregate phases through a decrease in energy gap ΔEST and an increase in the relative reorganization energy through bending the angle ∠C2−Cu−N1 for T1. We propose a pump−probe time-resolved infrared spectroscopy study to verify the mechanism. These findings can clarify the ongoing dispute over the understanding of the high TADF quantum efficiency for two-coordinate metal complexes.

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2021/03/15

 

 

Congratulations to Sheng Huang on his published paper in J. Mater. Chem. A!

Integration of ferroelectricity into van der Waals heterostructures offers additional opportunities to control over the properties and functionalities of heterostructures by switching the direction of polarization via an external electric field. To discover potential ferroelectric monolayers that exhibit out-of-plane electric polarizations, we screen a family of metal phosphorus trichalcogenides M1M2P2X6 with M1= Cu/Ag, M2 = In/Bi, X = S/Se using density functional theory calculations. We predict room-temperature ferroelectricity/ in CuInP2S6 and CuBiP2S6 monolayers with out-of-plane polarizations (Ps) of 0.59 μC cm-2 and 0.35 μC cm-2, respectively. The strong metal-chalcogenide M1-X bond in the two Cu and S-based systems is responsible for their high phase transition temperatures. The polarizations in ferroelectric monolayers can persist in van der Waals heterostructures, and band gaps as well as band alignment of the heterostructures can be tuned by switching the polarization direction. Finally, we demonstrate that both visible light absorption and type-II band alignment facilitating fast charge separation can be realized in CuInP2S6/Mn2P2S6 and CuInP2S6/Zn2P2Se6 ferroelectric heterostructures, which are promising for applications in photocatalytic water splitting.

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2021/03/15

 

 Congratulations to Lu Wang on her published paper in J. Phys. Chem. A!

The thermally activated delayed fluorescence (TADF) phenomenon has attracted increasing attention because it can harvest 100% of the electro-pumped carriers to form singlet bound excited state for fluorescence. It is generally believed that the small energy gap between S1 and T1 (ΔEST) is essential for TADF to facilitate the reverse intersystem crossing (rISC). However, for a few donor-acceptor (D-A) organic compounds with small ΔEST, the TADF phenomenon is absent, indicating that ΔEST might not be a good molecular descriptor. Here, using our self-developed thermal vibration correlation function (TVCF) formalism in combination with quantum chemistry calculations, we revisit the key factors that dominate the TADF property for 11 D-A systems with small ΔEST. Based on our theoretical results in comparison to experiments, we conclude that the activation energy ΔG is a good molecular descriptor to characterize the TADF performance because a significantly better linear relationship is observed between ΔG and the rISC rate constant (krISC) compared to that between ΔEST and krISC. These findings provide deeper understanding of the TADF mechanism, shedding light on the molecular design of high-performance TADF materials.

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2020/03/15

 

 

 

Congratulations to Dr Qi Ou on her published paper in J. Phys. Chem. Lett.!

Recently, Wang and co-workers carried out frontier molecule orbital engineering in the design of m-Cz-BNCz, a thermally activated delayed fluorescence (TADF) molecule that emits pure green light at an external quantum efficiency of 27%. To further understand the underlying molecular design principles, we employed four advanced electronic structure analysis tools. First, an absolutely localized molecular
orbitals (ALMO-) based analysis indicates an antibonding combination between the highest occupied molecular orbitals (HOMOs) of the donor 3,6-di-tert-butylcarbazole fragment and the acceptor BNCz fragment, which raises the HOMO energy and red-shifts the fluorescence emission wavelength. Second, excitation energy component analysis reveals that the S1−T1 gap is dominated by two-electron components of the excitation energies. Third, charge transfer number analysis, which is extended to use fragment-based Hirshfeld weights, indicates that the S1 and T1 excited states of m-Cz-BNCz (within time-dependent density functional theory) have notable charge transfer characters (27% for S1 and 12% for T1). This provides a balance between a small single-triplet gap and a substantial fluorescence intensity. Last, a vibrational reorganization energy analysis pinpoints the torsional motion between the BNCz and Cz moieties of m-Cz-BNCz as the source for its wider emission peak than that of p-Cz-BNCz. These four types of analyses are expected to be very valuable in the study and design of other TADF and functional dye molecules.

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2021/02/17

 

 

 

Congratulations to Qian Peng on her published cover paper in Accounts of Chemical Research!

Room-temperature phosphorescence (RTP) with long afterglow from purely organic molecular aggregates has recently attracted great amount of investigations, because traditionally only inorganic and transition-metal complexes can emit phosphorescence at room temperature. In this account, the underling mechanism of such aggregation induced organic RTP through theoretical investigation and quantum chemistry calculations by invoking intermolecular interaction effects has been unveiled, and the molecular descriptors to characterize the phosphorescence efficiency and lifetime for molecular design of RTP materials have been identified, which are expected to play important roles in the machine-learning-based molecular screening in the future.

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2021/02/14

 

 

Congratulations to Dr Xingliang Peng on his published paper in Nanoscale!

A multiscale approach by combining molecular dynamics simulations, quantum mechanics calculations and kinetic Monte-Carlo simulations has been applied to investigate the influence of dynamic and static disorder on the hole mobilities of four BTBT isomers. It is found that the dynamic disorder of transfer integral tends to decrease the mobility for quasi-1D (quasi one-dimensional) BTBT1 and BTBT4 isomers and increase the mobility for 2D (two-dimensional) BTBT2 and BTBT3 isomers, while the dynamic disorder of site energy tends to decrease mobility for all the four isomers; however, the reduction in 2D molecules is much less than that in quasi-1D molecules. Results show that trap defects could reduce the mobility for both the quasi-1D and 2D molecular structures significantly, even to several orders of magnitude.

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2020 News


2020/12/10


 

 

 

Congratulations to Tong Jiang on his published cover paper in CHEMICAL JOURNAL OF CHINESE UNIVERSITIES!

Density matrix renormalization group(DMRG)has been developed for electron correlation in low dimensional system and has been quickly applied to quantum chemistry as a powerful method for electronic structure calculation and for quantum dynamics of complex system. After more than 20 years of development,a series of effective methods for calculating dynamic response properties within DMRG have been developed and extensively applied for spectroscopy. The paper overviews the main features of DMRG, including its matrix product state(MPS)formulation, as well as the DMRG algorithms in frequency domain to solve the response properties both for zero temperature and finite temperature, and also introduces several most relevant applications in electronic correlation problems and electron-phonon correlation problems.

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[2020/9/23]

 

Congratulations to Dr Yu Wang on her published paper in J. Mater. Chem. A!

It is generally perceived that a fast reverse intersystem crossing rate of T1 / S1 (krisc) is crucial for efficient organic thermally activated delayed fluorescence (TADF) emitters, the paper demonstrates the nonradiative decay rate of T1 / S0 (kTnr) for transition metal complexes that is even more important.

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[2020/9/16]

 

 

Congratulations to Dr Qi Ou on her published paper in Nature Communications !

Electrically pumped organic lasing is one of the most challenging issues in organic optoelectronics. The article present a systematic theoretical investigation to screen out electrical pumping lasing molecules over a wide range of organic materials. With the electronic structure information obtained from time-dependent density functional theory, multiple photophysical parameters of a set of optical pumping organic laser are calculated with MOMAP to judge whether the electrically pumped lasing conditions can be satisfied, namely, to avoid reabsorption from excitons and/or polarons, and the accumulation of triplet excitons.

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[2020/9/11]


 

 

 

 

Congratulations to Dr Qi Ou on her published cover paper in J. Phys. Chem. Lett.!

Accurate theoretical description of the electronic structure of boron dipyrromethene (BODIPY) molecules has been a challenge, let alone the prediction of fluorescence quantum efficiency. The Letter show that the electronic structures of BODIPYs can be accurately evaluated via the spin-flip time-dependent density functional theory with the B3LYP functional.

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[2020/7/3]

 

 

 

 

 

 

 


 

Congratulations to Weitang Li on his published cover in J. Phys. Chem. Lett.!

The charge transport mechanism and carrier mobility in organic semiconductors are studied by the numerically exact time-dependent density matrix renormalization group method. The method bridges the gap between hopping/band picture and predicts band-like transport behavior for the rubrene crystal.

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[2020/6/21]

 

Congratulations to Weitang Li for his new paper has been published in J. Phys. Chem. Lett.!

Congratulations to Weitang Li for his new paper on Finite-Temperature TD-DMRG for the Carrier Mobility of Organic Semiconductors has been published in J. Phys. Chem. Lett.

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[2020/4/30]

 

Congratulations to Tong Jiang for his new paper has been published in J. Phys. Chem. Lett.!

Congratulations to Tong Jiang for his new paper on Finite Temperature Dynamical Density Matrix Renormalization Group for Spectroscopy in Frequency Domain has been published in J. Phys. Chem. Lett.

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[2020/4/21]

 

Congratulations to Yajing Sun for his new paper has been published in ChemPhysChem!

Congratulations to Yajing Sun for his new paper on Computational Study on the Charge Transport and Optical Spectra of Anthracene Derivatives in Aggregates has been published in ChemPhysChem.

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[2020/1/15]

 

 

Congratulations to Weitang Li for his new paper has been published in J. Chem. Phys.!

Congratulations to Weitang Li for his new paper on Numerical assessment for accuracy and GPU acceleration of TD-DMRG time evolution schemes has been published in Inorg. Chem.

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 2019 News


[2019/12/3]

 

 

 

Congratulations to Shiyun Lin for his new paper has been published in Inorg. Chem.!

Congratulations to Shiyun Lin for his new paper on Strong Solid-State Fluorescence Induced by Restriction of the Coordinate Bond Bending in Two-Coordinate Copper(I)–Carbene Complexes has been published in Inorg. Chem.

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[2019/12/3]

 

 

Congratulations to Huili Ma for his new paper has been published in Journal of Physical Chemistry Letters!

Congratulations to Huili Ma for his new paper on Hydrogen Bonding-Induced Morphology Dependence of Long-Lived Organic Room-Temperature Phosphorescence has been published in Journal of Physical Chemistry Letters.

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 [2019/09/01]

 

Welcome Dr Xingliang Peng, Dr Qi Ou, Dr Yu Wang, Mr Hengrui Yang and Mr Yufei Ge to join the Shuaigroup!

 [2019/05/29]

 

Congratulations to Zhen Wang !
 
Congratulations to Zhen Wang for completing his PhD Dissertation Defense !

 [2019/05/29]

 

Congratulations to Jahanzeb Khan !
 
Congratulations to Jahanzeb Khan for completing his PhD Dissertation Defense !

[2019/05/29]

 

Congratulations to Yajing Sun !
 
Congratulations to Yajing Sun for completing her PhD Dissertation Defense !

[2019/05/29]

 

Congratulations to Jiajun Ren !
 
Congratulations to Jiajun Ren for completing his PhD Dissertation Defense !

[2019/05/20]

 

 

Congratulations to Yunpeng Liu for his new paper has been published in Journal of Physical Chemistry Letters!

Congratulations to Yunpeng Liu for his new paper on boosting the Seebeck coefficient for organic coordination polymers has been published in Journal of Physical Chemistry Letters.

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[2019/05/18]

 

Congratulations to Yajing Sun for her new paper has been published in Journal of Physical Chemistry C!

Congratulations to Yajing Sun for her new paper on the role of phonon–electron coupling in reducing lattice thermal conductivity has been published in Journal of Physical Chemistry C.

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[2019/05/18]

Congratulations to Wen Shi for his new paper has been published in Advanced Electronic Materials!

Congratulations to Wen Shi for his new paper on high-performance thermoelectric materials has been published in Advanced Electronic Materials.

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[2019/03/29]

Congratulations to Yuqian Jiang for her new paper has been published in Journal of Chemical Theory Computation!

Congratulations to Yuqian Jiang for her new paper on the charge transport in organic semiconductors has been published in Journal of Chemical Theory Computation.

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[2019/02/10]

Congratulations to Tian Zhang for her new paper has been published in Journal of Materials Chemistry C!

Congratulations to Tian Zhang for her new paper on organic mechano-responsive luminescent materials has been published in Journal of Materials Chemistry C.

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 [2019/01/18]

 

 

 

课题组在有机室温磷光材料理论设计方面取得重要进展

由于纯有机分子的旋轨耦合比较弱,长期以来有机材料室温下没有磷光。最近,一系列实验发现在固相下纯有机化合物也会表现出高效室温磷光,但其发光效率和寿命不可兼得。在帅志刚和彭谦的指导下,博士后马会利等人提出了一对分子描述符来分别表征磷光效率和寿命。由羰基和π-共轭片段组成的典型RTP体系,其激发态可以视为n→π*跃迁和π→π*跃迁两组分的组合。他们基于光物理原理,特别是El-Sayed规则,引入了一对分子描述符 (γ, β), 其数值的大小与固相下单/三线激发态的(n, π*)和(π, π*)跃迁成分有关。结合量子力学/分子力学(QM/MM)方法,他们揭示了分子描述符 (γ, β) 与磷光效率和寿命以及旋轨耦合之间的关系。他们提出,大的γ和β值有利于有机材料中强的、长寿命的RTP。该研究以题为“Efficient and Long-lived Room Temperature Organic Phosphorescence: Theoretical Descriptors for Molecular Designs”发表于Journal of the American Chemical Society,2019,141,1010-1015。

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