Elaborating H-bonding effect and excited state intramolecular proton transfer of 2-(2-hydroxyphenyl)benzothiazole based D-π-A fluorescent dye.

2-(2-Hydroxyphenyl)benzothiazole (HBT) derivatives with donor-π-acceptor (D-π-A) structure have received extensive attention as a class of excited state intramolecular proton transfer (ESIPT) compounds in the fields of biochemistry and photochemistry. The effects of electron-donors (triphenylamine and anthracenyl), the position of substituents and solvent polarity on the fluorescence properties and ESIPT mechanisms of HBT derivatives were investigated through time-dependent density functional theory (TDDFT) calculations. Potential energy curves (PECs) and frontier molecular orbitals (FMOs) reveal that the introduction of the triphenylamine group on the benzene ring enhances intramolecular HB, thereby benefiting the ESIPT process.

Enhancing Burning Rate of Ammonium Nitrate by Ammonia Borane: Mechanism from Reactive Molecular Dynamics Simulation.

The development of ammonium nitrate (AN)/ammonia borane (AB) as a green propellant is crucial for their applicability in different engines. This study investigates the release patterns of small products, particularly nitrogen-containing molecules, during the initial pyrolysis of AN/AB at low and high pressures using ReaxFF MD simulations. Compared with pure AN, the addition of AB gives the hybrid system enhanced reactivity, leading to faster decomposition and higher energy release.

Theoretical study on optimizing dipeptidomimetic isocyanonaphthalene chemosensor and the fluorescence mechanism for detecting Hg.

The excited (S) state charge distribution characteristics and fluorescence mechanism of fluorescence probes benzyl (6-cyano-2-naphthoyl)-L-valinate (NPI) and benzyl (6-amino-2-naphthoyl)-L-valinate (NPA) have been discussed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Further analysis by constructing a torsional potential energy curve (PEC) shows that a well-defined minimum energy conformation is observed when the C-C single bond between the valine benzyl ester and naphthalene ring in NPI rotates. For NPA, the most stable conformation is the naphthalene ring conformation with dihedral angle NCCC of -30.

Computational method on highly efficient D-π-A-π-D-based different molecular acceptors for organic solar cells applications and non-linear optical behaviour.

Eight molecular structures (BT-A1 to BT-A8) with high-performance non-fullerene acceptor (NFA) were selected for organic solar cells (OSCs) and non-linear optical (NLO) applications. Their electronic, photovoltaic (PV) and optoelectronic properties were tuned by adding powerful electron-withdrawing groups to the acceptor (A) of the D-π-A-π-D structure. Using time-dependent density functional theory (TD-DFT) techniques, based on the laws of quantum chemical calculations, the absorption spectra, stability of the highest and lowest-energy molecular orbitals (HOMO/LUMOs), electron density, intramolecular charge transfer (ICT), transition density matrix (TDM), were examined.

Theoretical investigation on regulating photophysical properties and proton transfer behavior by electronegativity for near-infrared emitting styryl dyes.

Our main focus is to explore the atomic electronegativity-dependent photoinduced behavior of styryl derivatives (HBO, HBS, and HBSe). The results of structural parameter calculation by the DFT method show that the intramolecular hydrogen bonds of normal and tautomer form are strengthened and weakened, respectively, in an excited state (S), which is conducive to the excited intramolecular proton transfer (ESIPT) process. The enhancement of excited hydrogen bond is beneficial to the ESIPT process from the aspects of infrared vibration frequency (IR), Mulliken's charge analysis, and density gradient reduction (RDG).

Theoretical design and evaluation of efficient small donor molecules for organic solar cells.

Context: The development of high-efficiency photovoltaic devices is the need of time with increasing demand for energy. Herein, we designed seven small molecule donors (SMDs) with A-π-D-π-A backbones containing various acceptor groups for high-efficiency organic solar cells (OSCs). Molecular engineering was performed by substituting the acceptor group in the synthesized compound (BPR) with another highly efficient acceptor group to improve the photoelectric performance of the molecule.

Crystal morphology prediction of CL-20 and 1,4-DNI co-crystal at different temperatures.

Context: The morphologies of hexanitrohexaazaisowurtzitane (CL-20) and 1,4-dinitroimidazole (1,4-DNI) co-crystal under vacuum or solvent at different temperatures were predicted. The CL-20/1,4-DNI co-crystal has six important growth crystal planes: (002), (011), (101), (11‒1), (110), (111). The areas of (002), (101), and (011) planes account for a relatively large proportion, which are important crystal planes that affect the crystal morphology.

Decomposition mechanism of 1,3,5-trinitro-2,4,6-trinitroaminobenzene under thermal and shock stimuli using ReaxFF molecular dynamics simulations.

To obtain atomic-level insights into the decomposition behavior of 1,3,5-trinitro-2,4,6-trinitroaminobenzene (TNTNB) under different stimulations, this study applied reactive molecular dynamics simulations to illustrate the effects of thermal and shock stimuli on the TNTNB crystal. The results show that the initial decomposition of the TNTNB crystal under both thermal and shock stimuli starts with the breakage of the N-NO bond. However, the C ring in TNTNB undergoes structural rearrangement to form a C-C bicyclic structure at a constant high temperature.

Facile synthesis of triazine-based microporous organic network for high-efficient adsorption of flumequine and nadifloxacin: A comprehensive study on adsorption mechanisms and practical application potentials.

Flumequine (FLU) and nadifloxacin (NAD), as emerging contaminants, have received extensive attention recently. In this study, a triazine-based microporous organic network (TMON) was synthetized and developed as an excellent adsorbent for FLU and NAD. The adsorption behavior and influence factors were investigated in both single and binary systems.

Nitrogen-rich polycyclic pentazolate salts as promising energetic materials: theoretical investigating.

Pentazolate (cyclo-N) salts are nitrogen-rich compounds with great development potential as energetic materials due to their full nitrogen anion. However, the densities of available N salts are generally low, which seriously lowers their performances. It is necessary to screen out cyclo-N salts with high density.

Atomic perspective revealing for combustion evolution of nitromethane/nano-aluminum hydride composite.

Adding aluminum hydride (AlH) into energetic materials (EMs) can improve their combustion and energy performance effectively. However, the potential mechanism of AlH on EMs is still unclear. Based on the ReaxFF-lg method, the thermal decomposition of nitromethane/nano-aluminum hydride (NM/nano-AlH) composites were studied.

Encapsulating aluminum nanoparticles into carbon nanotubes for combustion: a molecular dynamics study.

Metal nanoparticles are easily deactivated by migration-aggregation in combustion. Encapsulated nanoparticles are one of the tools for coping with the stability challenges of metal nanoparticles. The self-assembly details of aluminum nanoparticles (ANPs) encapsulated into carbon nanotubes (CNTs) were demonstrated by molecular dynamics simulations.

Coarse-grained force-field for large scale molecular dynamics simulations of polyacrylamide and polyacrylamide-gels based on quantum mechanics.

We developed a new coarse-grained (CG) molecular dynamics force field for polyacrylamide (PAM) polymer based on fitting to the quantum mechanics (QM) equation of state (EOS). In this method, all nonbond interactions between representative beads are parameterized using a series of QM-EOS, which significantly improves the accuracy in comparison to common CG methods derived from atomistic molecular dynamics. This CG force-field has both higher accuracy and improved computational efficiency with respect to the OPLS atomistic force field.

Theoretical research about nonmetallic energetic salts with pentazolate anion.

Significant progress has been made in the synthesis of nitrogen-rich high-energy salts by pairing pentazolate anion (cyclo-N) with different cations since cyclo-N was synthesized. It is difficult to screen out cyclo-N salts with high energy quickly and effectively in experiment, while theoretical research can realize this goal. Herein, nineteen high-energy salts, which were composed of tetrazole cation and cyclo-N anion, were designed.

Reactive molecular dynamics simulation of thermal decomposition for nitromethane/nano-aluminum composites.

The thermal decomposition of pure nitromethane (NM) and NM/nano-aluminum (Al) composites was simulated by reactive molecular dynamics with ReaxFF-lg corrected force field parameters. The initial decomposition pathway of NM molecules in pure NM is C-N bond rupture. However, NM is decomposed early by the initial pathway of N-O bond rupture when it mixes with nano-Al because of the strong attraction of Al to O.

Theoretical Study of Effects of Anchoring Groups on Photovoltaic Properties of a Triarylamine-Based p-Type Sensitizer.

The effects of anchoring groups on triarylamine-based p-type dyes were studied by substituting the strong electron-withdrawing carboxyl group with the weak electron-withdrawing pyridyl and the electron-rich catechol groups. Judged by the index , the charge separation would be improved greatly when the carboxyl group of is replaced by the pyridyl or catechol groups. Although carboxyl as an anchoring group lowers the HOMO energy and facilitates the hole injection in comparison with pyridyl and catechol groups, the weak electron-withdrawing pyridyl and the electron-rich catechol groups facilitate the charge separation.

Thermal Decomposition Mechanism of 1,3,5,7-Tetranitro-1,3,5,7-tetrazocane Accelerated by Nano-Aluminum Hydride (AlH): ReaxFF-Lg Molecular Dynamics Simulation.

ReaxFF-low-gradient reactive force field with CHONAl parameters is used to simulate thermal decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and AlH composite. Perfect AlH and surface-passivated AlH particles were constructed to mix with HMX. The simulation results indicate HMX is adsorbed on the surface of particles to form O-Al and N-Al bonds.

Crystal morphology prediction of 2,2',4,4',6,6'-hexanitrostilbene (HNS) by molecular scale simulation.

The spiral growth model was applied to predict the crystal morphology of 2,2',4,4',6,6'-hexanitrostilbene (HNS). We selected solvents of N,N-dimethylformamide (DMF), N-methyl pyrrolidone (NMP), and nitric acid (NA) to control the crystal morphologies of HNS. Molecular dynamic simulations were used to relax the constructed interface model.

Theoretical Investigation of Energetic Salts with Pentazolate Anion.

Energetic salts based on pentazolate anion (-N) have attracted much attention due to their high nitrogen contents. However, it is an enormous challenge to efficiently screen out an appropriate cation that can match well with -N. The vertical electron affinity () of the cations and vertical ionization potential () of the anions for 135 energetic salts and some -N salts were calculated by the density functional theory (DFT).

Design of high performance p-type sensitizers with pyridinium derivatives as the acceptor by theoretical calculations.

Based on triphenylamine as an electron donor and thiophene as a π-linker, Series P and A p-type sensitizers were designed to investigate the effects of the different acceptors on the properties of the sensitizers. The optimized molecular structures, electronic and optical properties were investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). The results showed that the properties of the dyes can be tuned by the introduction of the different electron-withdrawing groups to the N atom in the pyridinium acceptor.

Crystal Morphology Prediction and Anisotropic Evolution of 1,1-Diamino-2,2-dinitroethylene (FOX-7) by Temperature Tuning.

Temperature-induced morphological changes are one of the strategies for designing crystal shapes, but the role of temperature in enhancing or inhibiting crystal growth is not well understood yet. To meet the requirements of high density and low sensitivity, we need to control the crystal morphology of the energetic materials. We studied the crystal morphology of 1,1-diamino-2,2-dinitroethylene (FOX-7) in dimethyl sulfoxide/water mixed solvent by using the modified Hartman-Perdok theorem.

Reactive molecular dynamics simulation of the high-temperature pyrolysis of 2,2',2'',4,4',4'',6,6',6''-nonanitro-1,1':3',1''-terphenyl (NONA).

2,2',2'',4,4',4'',6,6',6''-Nonanitro-1,1':3',1''-terphenyl (NONA) is currently recognized as an excellent heat-resistant explosive. To improve the atomistic understanding of the thermal decomposition paths of NONA, we performed a series of reactive force field (ReaxFF) molecular dynamics simulations under extreme conditions of temperature and pressure. The results show that two distinct initial decomposition mechanisms are the homolytic cleavage of the C-NO bond and nitro-nitrite (NO → ONO) isomerization followed by NO fission.

Molecular dynamics simulation on the reaction of nano-aluminum with water: size and passivation effects.

The reaction of aluminum and water is widely used in the field of propulsion and hydrogen production, but its reaction characteristics at the nanometer scale have not been fully studied. In this paper, the effect of particle size and surface passivation of aluminum particle on the reaction mechanism was studied by using reactive molecular dynamics (RMD) simulation. The reduction of aluminum particle size can accelerate the reaction rate in the medium term (20-80 ps) due to the increase of activity, but it also produces an agglomeration effect as the temperature increases.

Molecular Modeling on Morphology of 3,4-Bis(3-nitrofurazan-4-yl)furoxan Crystals in Dichloroethane or Benzene Mixture Solvents.

According to the experiments, DNTF crystallizes in benzene/methylbenzene (1:1), benzene/methylbenzene/ethanol (2:3:5), and sym-dichloroethane solvents into two similar crystal shapes, namely strip and tetrahedral. There is a possibility that solvent changes the crystal morphology. In order to explain this phenomenon, the DNTF growth interface model was constructed according to the actual solution environment.

Theoretical study of nitrogen cation modified aromatics containing thiophene as π-linker for p-type photosensitizers.

On the basis of triphenylamine as an electron donor with attachment of two -COOH anchoring groups and dicyanovinyl as acceptor, ten dyes with D-π-A structures were designed to investigate the effects of different π-linker groups on the properties of the sensitizers, especially the influence of the π-linkers containing nitrogen cation (N). The optimized structures and electronic and optical properties were investigated by the density functional theory (DFT) and time-dependent DFT (TD-DFT). The results show that all the investigated dyes can be used as dye sensitizers for the p-type dye-sensitized solar cells (DSSCs) except one dye which contains two N.