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First-principles Simulation of Elastic Constants and Electronic Properties of GaN
摘要： The electronic and structural properties and elastic constants of the wurtzite phase of GaN, was investigated by computer simulation at Density Functional Theory level, with B3LYP and B3PW hybrid functional. The electronic properties were investigated through the analysis of the band structures and density of states, and the mechanical properties were studied through the calculus of the elastic constants: C11, C33, C44, C12, and C13. The results show that the maximum of the valence band and the minimum of the conduction band are both located at the Γ point, indicating that GaN is a direct band gap semiconductor. The following constants were obtained for B3LYP and B3PW (in brackets): C11 = 366.9 [372.4], C33 = 390.9 [393.4], C44 = 99.1 [96.9], C12 = 143.6 [155.2], and C13 = 107.6 [121.4].
关键词： periodic calculations,GaN,elastic constant,B3PW,B3LYP
更新于2025-09-23 15:21:01
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Hydrogen bonding between ethynyl aromates and triethylamine: IR spectroscopic and computational study
摘要： Ethynylpyridines (EPs) and ethynylbenzene (EB) are multifunctional systems able to participate in hydrogen-bonded complexes as both donors and acceptors of the H-atom. Their structures and stabilities are mainly a function of the hydrogen-bonding properties of the partner in the complex and the surroundings in which the complexation occurs. In this paper, IR spectroscopy and quantum chemical calculations are employed to characterize hydrogen-bonded complexes of 2- and 3-EP and EB with triethylamine (TEA) in tetrachloroethene (C2Cl4) solution. The formation of ≡C?H···N hydrogen bonds is experimentally confirmed by the appearance of TEA concentration-dependent signals in the IR spectra of the EPs and EB. Along with the signals due to unassociated ≡C?H and C≡C oscillators (2-EP: 3308 cm–1 and 2120 cm–1; 3-EP: 3308 cm–1 and 2116 cm–1; EB: 3313 cm–1 and 2113 cm–1) weak, red-shifted signals arise at ~3215 ± 5 cm–1 and ~2105 ± 5 cm–1 which are assigned to the stretching vibrations of hydrogen-bonded ≡C?H··· and C≡C··· oscillators, respectively. This result is at variance with those of previous investigations of EB and TEA in the gas phase. In the 2-EP···TEA complex these bands remain at the same position with increasing TEA concentration. However, in the 3-EP···TEA and EB···TEA complexes the ≡C?H··· stretching band demonstrates a slightly reduced red-shift as the TEA concentration increases, whereas the C≡C··· stretching band absorbs at the same wavenumber in the investigated TEA concentration range. The results of B3LYP-D3 calculations indicate that complexes with more or less linear ≡C?H···N intermolecular hydrogen bonds are more stable than other, dispersion-driven complexes. Complexes with the Cs symmetrical TEA conformer are predicted to have larger binding energy than those formed with the C3 and C1 symmetrical conformers. The predicted IR spectral shifts are slightly different for complexes with the three different TEA conformers. Association constants of hydrogen-bonded complexes at 26 °C are estimated to be ~0.1 mol–1 dm3.
关键词： triethylamine,hydrogen bonding,ethynyl aromates,IR spectroscopy,B3LYP-D3 calculations
更新于2025-09-23 15:21:01
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The photophysical properties and electronic structures of bis[1]benzothieno[6,7-d:6',7'-d']benzo[1,2-b:4,5-b']dithiophene (BBTBDT) derivatives as hole-transporting for organic light-emitting diodes (OLEDs)
摘要： By using the quantum methods DFT and TD-DFT in this paper, the optoelectronic properties and electronic structures of eight compounds Ci (i=1-8) based on bis[1]benzothieno[6,7-d:6',7'-d']benzo[1,2-b:4,5-b']dithiophene (BBTBDT) with D-π-D structure for Ci (i=1-5); and D-π-A for Ci (i=6-8) have been calculated and discussed theoretically in the aim to consider them as hole-transporting materials (HTM) in OLEDs. The calculated electronic levels by B3LYP of studied compounds show that the proper energy of Ci (i=6-8) is so matching for efficiency injecting into hole-injection layer (HIL). The compounds having D-π-A structure seem more efficient than those having D-π-D structure. The optoelectronic properties for studied compounds obtained by TD-CAM-B3LYP elucidate that C6, C7 and C8 compounds behave as electron donating molecules and induce charge transfer character in the UV-visible absorptions and emission electronic spectra. Furthermore, the calculated reorganization energies, ionization potential (IP) and electron affinity (EA) also provide that the extended C6, C7 and C8 compounds have the highest charge-transporting ability among all compounds. It is found that the D-π-A more influence on the electronic and optoelectronic properties than the D-π-D structure. The assumed compound C7 is found to be a good candidate for blue-emitting material. Understanding these properties is important to design HTMs with exceptional properties, such as stability and high efficiency.
关键词： B3LYP,DFT,bis[1]benzothieno[6,7-d:6',7'-d']benzo[1,2-b:4,5-b']dithiophene (BBTBDT),OLEDs
更新于2025-09-11 14:15:04
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Theoretical calculations of electron paramagnetic resonance parameters of succinimide radical
摘要： The analysis of the molecular structure and spectral properties of succinimide can be used as a reliable tool in understanding all interactions between this molecule with the other chemicals. For this reason, we first examined the conformational variety of succinimide in free state through an energy minimization calculations using the spartan 08 software. This preliminary calculation confirmed that free succinimide molecule has only one stable conformer at room temperature and the dipole moment and energy values of this conformer are 2.221 Debye and -360.779 Hartree, respectively. The optimized geometry of the conformer was then obtained at B3LYP/6-311++G(d,p) level of theory by using the Gaussian 03 software. In the next step of the study, eleven radicals were formed from this one conformer of succinimide by removing an hydrogen atom or changing its location in the molecule. For each radical structure, the corresponding Electron Paramagnetic Resonance (EPR) parameters were calculated using the DFT/B3LYP method and TZVP basis set and then they were compared with the corresponding experimental values. The “g” value (EPR parameter) calculated in this study for the model radical (Rad 6) is 2.00388 and in good agreement with the corresponding experimental value (2,00339) previously reported in the literature for the radical form of succinimide.
关键词： DFT,B3LYP,succinimide,TZVP,electron paramagnetic resonance
更新于2025-09-04 15:30:14