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In the ZINC20 database, with the aid of maximum substructure searches, common substructures were obtained from molecules with high-strain-energy and combustion heat values, and further provided domain knowledge on how to design high-energy-density hydrocarbon (HEDH) fuels. Notably, quadricyclane and syntin could be topologically assembled through these substructures, and the corresponding assembled schemes guided the design of 20 fuel molecules (ZD-1 to ZD-20). The fuel properties of the molecules were evaluated by using group-contribution methods and density functional theory (DFT) calculations, where ZD-6 stood out due to the high volumetric net heat of combustion, high specific impulse, low melting point, and acceptable flash point. Based on the neural network model for evaluating the synthetic complexity (SCScore), the estimated value of ZD-6 was close to that of syntin, indicating that the synthetic complexity of ZD-6 was comparable to that of syntin. This work not only provides ZD-6 as a potential HEDH fuel, but also illustrates the superiority of learning design strategies from the data in increasing the understanding of structure and performance relationships and accelerating the development of novel HEDH fuels. [ABSTRACT FROM AUTHOR]

The deviations of gas phase enthalpy of formation predicted by density functional theory on the fluorine containing system are larger than those on other systems in most cases. Therefore, an enthalpy of formation test set composed of 41 organic fluorine containing compounds is proposed, and in this work it is called OFCC41 test set. Twenty exchange‐correlation functionals are estimated by CCSD(T)/CBS as benchmark. The first part of the results indicates that CAM‐B3LYP, ωB97X, and M06 are the most suitable functionals to predict enthalpies of formation for fluorine containing compounds. The remainder of this work is primarily concerned with diffuse basis sets and size‐dependent effects. Diffuse basis sets ma‐SVP and ma‐TZVP can generally improve the prediction performance. For very small molecules, using ma‐SVP is sufficient while for larger molecules more completed basis sets are demanded. Size‐dependent effect of prediction accuracy on different molecules is revealed by using a simple strategy, that the different sizes of molecules are distinguished with three intervals and given the corresponding mean absolute errors. This study provides a test set designed for organic fluorinated compounds and contributes to the selection of some functionals suitable for fluorine containing system. [ABSTRACT FROM AUTHOR]

The replacement of traditional polynitroarylenes by their fluorinated derivatives has attracted great attention due to the improvements on detonation performance caused by the fluorine effect. A straightforward synthesis of three novel fluorinated nitrotoluenes with different degrees of nitration was achieved under selected high temperatures. The fluorine exerted remarkable influence on the nitration process through the electron‐withdrawing effect and a mechanism of the transformation was proposed according to the experimental results. Thermal decomposition behavior of the fluorinated nitrotoluenes was investigated by differential scanning calorimetry and all the compounds showed ideal low melt points for the melt‐cast process. X‐ray analysis of the fluorinated derivatives were carried out as well as density functional calculations to establish the electronic density and electrostatic potential on the molecular surface of the optimized structures. The good thermal and detonation properties make the newly developed fluorinated nitrotoluenes possible replacements for trinitrotoluene and dinitrotoluene in the formation of melt‐cast energetic materials. A straightforward synthesis of three novel fluorinated nitrotoluenes with different degrees of nitration has been achieved under selected high temperatures (see figure). A single nitration product could be obtained under the new nitration conditions and good energetic properties such as low melting points and thermal stability of these energetic molecules render them excellent prospects in the formation of melt‐cast energetic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Due to structural tunability, high surface area, abundant pore structures, and abundant active sites, covalent heptazine frameworks (CHFs) constructed from heptazine and other molecular blocks are especially prominent. Here, we proposed a reaction-dependent strategy for designing two dimensional CHFs including high-throughput precursors screening, structure generation, and performance evaluation. Assuming that oxamide-like precursors can undergo the same thermal polymerization reaction as producing C 6 N 7 , seven precursors were screened from more than 109 molecules in the ZINC20 database in terms of molecular weight, number of substructures, shape index, and symmetry. Furthermore, CHF-L1 to CHF-L7 were constructed from urea and the seven precursors according to the topologically assembling scheme in thermal polymerization. The designed CHFs had band gaps ranging from 1.89 to 3.10 eV. Among them, CHF-L3 assembled structurally by urea and 1,2,4,5-tetrazine-3,6-dicarboxamide with the smallest bandgap and an oxidative potential bias of 1.38 V for oxygen evolution reaction was screened as the candidate with high oxidative ability. The negative formation energy based on the synthesis route indicated the synthetic feasibility of CHF-L3, and negative cohesive energy as well as the stable structure under ab initio molecular dynamics simulations confirmed the stability of CHF-L3. The present work is expected to provide a powerful design strategy for two-dimensional CHFs design and is broadly applicable to various computational covalent organic framework design systems and experimental studies. [ABSTRACT FROM AUTHOR]

Single-atom loading of the non-precious transition metals (M = Ti, V, Mn, and Fe) on the (100) surface of SrTiO 3 (STO) was theoretically investigated to evaluate the hydrogen evolution reaction (HER) with Gibbs free energy for hydrogen adsorption (∆ G H * ). V 1 -STO stood out owing to the ∆ G H * of − 0.08 eV, which was competitive to the metallic Pt with the value of − 0.09 eV. The d band center rationalized well the primary screening of single-atom non-precious transition metals on STO. Furthermore, strain engineering was applied to refine the HER performance of V 1 -STO. The tensile strain increased the ∆ G H * , while the compressed strain decreased the ∆ G H * . A new descriptor of the d orbital splitting (ε d − gap) was proposed to explain the optimization of the HER performance arising from the surface strains. This work conceives a combinational strategy to evaluate the HER performance, and may give guidance for the sequential design of HER catalysts. [Display omitted] • Screen the vanadium atom from four types of non-precious metal atoms to load on SrTiO 3 (100) surface for hydrogen evolution reaction. • Optimize the HER performance of V 1 -STO by further strain engineering. • Propose the material design strategy composed of first using d band center screening for suitable loading single atom type and then applying ε d − gap screening for optimal strain. [ABSTRACT FROM AUTHOR]

[Display omitted] • A combinatorial library design for the polycyclic energetic materials. • High-throughput screening to rapidly search aimed molecules from ∼105 energetic molecules. • The increased performance by the introduction of F-containing functional groups. • The featured fragments for promoting energy level. • High portability of the proposed workflow consisted of combinatorial library design and high-throughput screening. An advanced approach of combinatorial library design and high-throughput screening was developed to accelerate the search of CHONF-containing energetic materials with higher energy density than the current level. The combinatorial library was constructed with a large chemical space (∼105 molecules) via the fragment-based design, and four criteria, namely, oxygen-fluorine balance, detonation velocity, the drop weight impact height h 50 , and the synthesis difficulty, were proposed to achieve the high-throughput screening. About two thousand target molecules with some promising properties comparable to CL-20 were discovered primarily, and the effectiveness of the proposed approach was further verified by DFT calculations. Two of the top ten screened molecules have high detonation velocities approaching 9900 m/s. Besides, the relationship between structural fragments and properties was revealed based on the statistical analysis of a large number of molecules, showing the importance of featural fragments on promoting detonation performance. Hopefully, the exploration herein could enlighten new insight into the fast discovery of novel high-energy–density materials. [ABSTRACT FROM AUTHOR]