A Promising Thermodynamic Study of Hole Transport Materials to Develop Solar Cells: 1,3-Bis(N-carbazolyl)benzene and 1,4-Bis(diphenylamino)benzene

The thermochemical study of the 1,3-bis(N-carbazolyl)benzene (NCB) and 1,4-bis(diphenylamino)benzene (DAB) involved the combination of combustion calorimetric (CC) and thermogravimetric techniques. The molar heat capacities over the temperature range of (274.15 to 332.15) K, as well as the melting temperatures and enthalpies of fusion were measured for both compounds by differential scanning calorimetry (DSC). The standard molar enthalpies of formation in the crystalline phase were calculated from the values of combustion energy, which in turn were measured using a semi-micro combustion calorimeter. From the thermogravimetric analysis (TGA), the rate of mass loss as a function of the temperature was measured, which was then correlated with Langmuir’s equation to derive the vaporization enthalpies for both compounds. From the combination of experimental thermodynamic parameters, it was possible to derive the enthalpy of formation in the gaseous state of each of the title compounds. This parameter was also estimated from computational studies using the G3MP2B3 composite method. To prove the identity of the compounds, the 1H and 13C spectra were determined by nuclear magnetic resonance (NMR), and the Raman spectra of the study compounds of this work were obtained.

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy” Part II

Group contribution (GC) methods to predict thermochemical properties are eminently important to process design. We present a group contribution parametrization for the heat of formation of organic molecules exhibiting chemical accuracy, maximum 1 kcal/mol (4.2 kJ/mol) difference between experiment and model values while minimizing the number of parameters avoiding overfitting and therewith avoiding reduced predictability. Compared to the contemporary literature, this was successfully achieved by employing available literature high-quality and consistent experimental data, optimizing parameters group by group, and introducing additional parameters when chemical understanding was obtained supporting these. A further important result is the observation that the applicability of the group contribution approach breaks down with increasing substitution levels, i.e., more heavily alkyl-substituted molecules, the reason being a serious influence of substitution on the conformation of the flexible part of the entire molecule within particular valence angles and torsional angles affected, which cannot be accounted for by additional GC parameters with fixed numerical values.

GRAPHIC DEPENDENCES IN THE STUDY OF STRUCTURE - PROPERTIES OF GLYCOLS

Обсуждается взаимосвязь энтальпии образования двухатомных спиртов с различными факторами химического строения. Построены и проанализированы графические зависимости «Энтальпия образования - топологический индекс (ТИ)», «Энтальпия образования - номер изомера» и «Топологический индекс - номер изомера». Показано, что в одних случаях энтальпия образования хорошо коррелирует с ТИ, а в других случаях такой зависимости нет. The relationship between the enthalpy of formation of dihydric alcohols and various factors of chemical structure is discussed. Graphical dependencies "Enthalpy of formation - topological index (TI)", "Enthalpy of formation - isomer number" and "Topological index - isomer number" were constructed and analyzed. It was shown that in some cases the enthalpy of formation correlates well with TI, while in other cases there is no such dependence.

Structural Stability, Elasticity, Thermodynamics and Electronic Structures of L12-Type Ni3X (X=Al, Ti, V, Nb) Phases Under External Pressure Condition

In this paper, the impacts of external pressure on structural stability, elasticity, thermodynamics and relevant electronic structures of L12-type Ni3X (X=Al, Ti, V, Nb) phases were investigated using the first-principles methods. The lattice parameters(a,b,c) and volume(V) of the Ni3X phases decrease with increasing pressure. however, the elastic constants(Cij ), bulk modulus(B), shear modulus(G), and Young's modulus (E) increase. The calculated elastic constants indicate that the mechanical stability and ductility of Ni3X phases enhance with increasing pressure. The mechanical anisotropy of Ni3X phases are enhanced by the raised pressure. Electronic analysis shows that increase pressure makes Ni-d-orbital and X(X=Al, Ti, V, Nb) -d-orbital hybridization stronger and electron transfer increases. The sequence in regard to electron aggregation strength is Ni3Ti>Ni3Nb>Ni3V>Ni3Al. It is more directly reflected in the charge density difference maps. This is consistent with the analysis results of the enthalpy of formation(ΔH) and Debye temperature (ΘD).

Group Contribution Revisited: The Enthalpy of Formation of Organic Compounds with “Chemical Accuracy”

Group contribution (GC) methods to predict thermochemical properties are of eminent importance to process design. Compared to previous works, we present an improved group contribution parametrization for the heat of formation of organic molecules exhibiting chemical accuracy, i.e., a maximum 1 kcal/mol (4.2 kJ/mol) difference between the experiment and model, while, at the same time, minimizing the number of parameters. The latter is extremely important as too many parameters lead to overfitting and, therewith, to more or less serious incorrect predictions for molecules that were not within the data set used for parametrization. Moreover, it was found to be important to explicitly account for common chemical knowledge, e.g., geminal effects or ring strain. The group-related parameters were determined step-wise: first, alkanes only, and then only one additional group in the next class of molecules. This ensures unique and optimal parameter values for each chemical group. All data will be made available, enabling other researchers to extend the set to other classes of molecules.

Stability, Elastic and Electronic Properties of Ta2N by First-Principles Calculations

Owing to exploring the influence of the N atoms ordering in Ta2N compounds on their properties, the stability, elastic, and electronic properties of Ta2N compounds (Ta2N-I: P3¯ml and Ta2N-II: P3¯1m) were investigated using first-principles calculations based on density functional theory. Ta2N-II is energetically favorable according to the enthalpy of formation. Elastic constants were employed to reveal the stronger resistance to deformation, but weaker anisotropy, in Ta2N-II. A ductile-brittle transition was found between Ta2N-I (ductile) and Ta2N-II (brittle). The partial density of states showed a stronger orbital hybridization of Ta-d and N-p in Ta2N-II, resulting in stronger covalent bonding. The charge density difference illustrated the interaction of the Ta-N bond and electron distribution of Ta2N.

CORRELATIONS OF ENTHALPY EDUCATION - TOPOLOGICAL INDICES IN OF DIATOMIC ALCOHOLS

Обсуждается зависимость энтальпии образования двухатомных спиртов от топологических индексов (ТИ). Приведены ТИ и численные расчеты энтальпии образования гликолей, согласующиеся с экспериментом. The dependence of the enthalpy of formation of diatomic alcohols on the topological indices (TI) is discussed. TI and numerical calculations of the enthalpy of glycol formation are given, which are consistent with the experiment.

Computational Investigation and Screening of High-Energy-Density Materials: Based on Nitrogen-Rich 1,2,4,5-tetrazine Energetic Derivatives

In the present work, the geometric structures, the frontier molecular orbitals and the enthalpy of formation (HOF) of thirty six 1, 2, 4, 5-tetrazine derivatives (FTT) were systematically studied by using the B3LYP/6-311+G* method of density functional theory. Meanwhile, we also predicted the stability, detonation properties and thermodynamic properties of all FTT compounds. Results showed that all compounds have superior enthalpy of formation far exceeding that of common explosives RDX and HMX, ranging from 859kJ·mol-1-1532kJ·mol-1. In addition, the detonation performance (Q = 1426cal·g-1 -1804cal·g-1; P = 29.54GPa - 41.84GPa; D = 8.02km·s-1 - 9.53km·s-1), which is superior to TATB and TNT. It is also concluded that the introduction of coordination oxygen on the tetrazine ring can improve the HOF, density and detonation performance of the title compound, and -NH-NH- bridge and -NHNO2 group are also the perfect combination to increase these values. In view of stability, because of the fascinating performance of D3 (ρ =1.89g·cm-3; D = 9.38km·s-1; P = 40.13GPa)，E3(ρ = 1.87g·cm-3; D = 9.19km·s-1; P = 38.35GPa), F1 (ρ = 1.87g·cm-3; D = 9.42km·s-1; P = 40.23GPa) and F3 (ρ= 1.92g·cm-3; D = 9.53km·s-1; P = 41.84GPa), makes them very attractive to be chosen as HEDMs.