Multi‐expression programming based model for prediction of formation enthalpies of nitro‐energetic materials

There has been considerable interest in predicting the properties of nitro‐energetic materials to improve their performance. Not to mention insightful physical knowledge, computational‐aided molecular studies can expedite the synthesis of novel energetic materials through cost reduction labours and risky experimental tests. In this paper, quantitative structure–property relationship based on multi‐expression programming employed to correlate the formation enthalpies of frequently used nitro‐energetic materials with their molecular properties. The simple yet accurate obtained model is able to correlate the formation enthalpies of nitro‐energetic materials to their molecular structure with the accuracy comparable to experimental precision.     

片斷分子的建立和正則軌道的定域化

为了研究共轭分子的芳香性，我们建立了新的作用能分解法。该方法的核心是为任何一个共轭分子提供一个π和σ体系彻底分离的轨道基组{Φm^P-π，Φt^p-σ，Φf^P}。为此，放射环形环炔烃分子（D3h对称的）必须分割成3个乙炔片断（A，C，E）和3个乙烯片断（B，D，F），经的{Φm^P-π，Φt^p-σ，Φf^P}是由6个片断的轨道基组{ψk^P-π,ψn^P-σ，ψ‘s^P}(P=A,B,…，F）叠加而成。FMP-L和FMP-R（P=A，B，…，F）是片断P的两个片断分子，设它们C-HR键的键长分别是rR(P)和rL(P)。在定域化后，单占据轨道ψ‘s^P和参考氢原子HR占据轨道ψ‘A^H的总电子数∑qs(P) ∑qh(P)总是正确的，与rR(P)和rL(P)的取值无关。但是，{ψ‘s^P}的空间取向取决于rL(P)和rR(P)的值。在片断A和B中，RV（A）=（-V/A）=1.95153 0.50869*rR^V(A),RV(B)=1.94556 0.54823*rR^V(B),设RV=2,则rR^V(A)=0.9528NM,rR^V(B)=0.09930nm。另外，有条件地优化FMP-R可算得：rR^O(A)=0.10658NM,rR^O(B)=0.10888nm。当rR^V(P)和rR^O(P)确定后，可得到；qs^v(A)=6.05124-56.5228*rL^V(A),qs^V(B)=5.17915-47.0804*rL^V(B);qs^O(A)=5.81883-49.0924*rL^O(A),qs^O(B)=4.70043-39.0818*rL^O(B)。然后设qs(P)=qh(P)=(1/4)(∑qs(P) ∑qh(P))，可得到：rL^V(A)=0.08937nm,rL^V(B)=0.08678nm,rL^O(A)=0.09816nm,rL^O(B)=0.09297nm，再由rR^V(P)和rL^V(P)计算的{Φm^P-π，Φt^p-σ，Φf^P}^V中，每一对成键单占据轨道Φt^P的电子占据数Qi比较均匀合理，它的12个单占据轨道的电子总占数为∑Qt=12.3。另外，在由{Φm^P-π，Φt^p-σ，Φf^P}^V算得的FUL态中，轨道分布也是更好地满足FUL态的基本特征。所以rR^V(P)和rL^V(P)比rR^O(P)和rL^O(P)更为合理。     

The standard enthalpies of formation of some intermetallic compounds of early 4d and 5d transition metals by high temperature direct synthesis calorimetry

The standard enthalpies of formation of some intermetallic compounds of early 4d and 5d transition metals have been measured by high temperature direct synthesis calorimetry at 1373±2 K. The following results (in kJ/mol of atoms) are reported: ZrMn₂(−24.7±2.7); ZrMo₂(−5.8±5.3); Zr₁₁Os₄(−8.9±2.1); HfCr₂(−4.8±4.3); HfMn₂(−20.3±2.0); HfMo₂(−6.4±4.3); NbRh₃(−21.6±1.8); TaRh₃(−14.0±4.0).     

Pyrolysis mechanism of carbon matrix precursor cyclohexane--the formation of condensed-ring aromatics and the growing process of molecules

Based on the experiments, the UAM1 method was adopted to investigate benzene condensation of an important intermediate and the molecule growing mechanism during the cyclohexane pyrolysis process. The conclusions were drawn as follows: (1) from the viewpoint of thermodynamics, the condensation of benzene and C4H5* is a spontaneous reaction and the rising temperature will increase the spontaneous tendency of the reaction. (2) From the viewpoint of kinetic, the condensation of benzene and C4H5* is a two-step reaction. The rate-determining step is step 2 of hydrogen removal from intermediate C10H10 (I1) with the activation energy of 350.61 kJ/mol below 1473 K while the rate-determining step is step 1 that free radical C4H5* attacks benzene to form intermediate C10H10 (I1) with the activation energy DeltaE(0)(not equal to theta)=31.74 kJ/mol above 1473 K. (3) The space structure, electronic structure and thermodynamics parameters of molecular reaction of dense-ring aromatizing compounds can be used to replace the resonance energy and free valence to judge the activation of thermodynamic reaction of compounds. And (4) the analysis of the space structure, electronic structure and thermodynamic parameters show that the growing process of molecules with benzene used as initial reactants becomes more easier as the multi-ring aromatizing molecular system increases.     

Formation of prototypes and their confidence regions in classification and concept formation problems

We discuss a problem of formation of prototypes of classes of patterns. An approach studied here takes advantage of techniques of fuzzy sets in forming a variable perception perspective. This in turn implies that the prototypes of the classes are determined in a logical fashion by solving an optimization problem in the unit hypercube. Then the confidence intervals associated with the prototypes are computed in such a way that they reflect the geometry of the classes of the patterns and are directly implied by the value of the performance index achieved during the optimization process. Numerical studies applying synthetic and real-world data enhance capabilities of the approach studied.