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    DFT-based structural and energetic characterisation of nitrogen-rich tetrazine/triazine derivatives with Kamlet-Jacobs performance predictions
    (Taylor & Francis Ltd, 2026) Ekincioglu, Yavuz; Kepceoglu, Abdullah; Cakir, Zehra; Senturk, Sukru
    Nitrogen-rich heterocycles are attractive candidates for next-generation energetic materials because they can deliver high heats of formation while producing relatively benign, N2-rich decomposition products. In this work, three nitrogen-rich frameworks 3,6-bis(tetrazol-5-yl)-1,2,4,5-tetrazine (H2BTTz), 2,4,6-tris(tetrazol-5-yl)-1,3,5-triazine (H3TTT), and 2,3,5,6-tetra(tetrazol-5-yl)pyrazine (H4TTP) were investigated using a combined conformational sampling and density functional theory (DFT) approach. Initial conformational searches were carried out with the MMFF method, and the lowest-energy structures were optimised at the DFT/B3LYP/6-311++G(d,p) level a widely used compromise between accuracy and computational cost for nitrogen-rich energetic molecules. Electronic structure analyses included frontier molecular orbitals, Mulliken and natural population charges, and molecular electrostatic potential maps. Energetic performance was evaluated through heats of formation, detonation velocity and pressure, and impact sensitivity estimates. Topological descriptors such as ELF, LOL, and NCI were analyzed using Multiwfn program. The calculated HOMO - LUMO gaps (3.54-4.90 eV) indicate electronically stable molecular frameworks. Gas-phase formation enthalpies were converted to condensed-phase values using a sublimation correction, and detonation properties were estimated via the Kamlet-Jacobs equations. The predicted performance follows the order H4TTP > H(2)BTTz > H3TTT. Although their detonation performance is lower than that of FOX-7 and CL-20, these nitrogen-rich systems remain promising candidates for reduced-sensitivity energetic materials and merit further experimental investigation.
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    Nonlinear optical properties of KnCl (n=2-7) superalkali clusters
    (Iop Publishing Ltd, 2024) Senturk, Sukru; Fardad, Fraidoon; Ekincioglu, Yavuz
    The lowest energy structures along with the low lying isomer, stabilities, electronic properties, optical properties and nonlinear optical responses of KnCl (n = 2-7) clusters were studied within the density functional theory. The second order energy difference, dissociation energy and GH-L (HOMO-LUMO gap) point out that KnCl (n = 3, 5, 7) clusters are more stable. The calculated adiabatic ionization energies (AIE) for the KnCl (n = 2-6) clusters are in agreement with the measured ionization energies. The optical properties, namely optical electronegativity and refractive index, depends on the GH-L energy values. The K atom capped planar rhombus geometry of the K4Cl causes the noticeable vibrational frequency shift compared to the rest of IR spectra of the clusters. The first static hyperpolarizability (beta(o)) values are in the range of 2.33 x 10(-2.87)(3) x 10(4) au and the second static hyperpolarizability varies between 5.74 x 10(6) au and 38.9 x 10(6) au for the cluster. The nonlinear optical response is due to the superalkali nature of KnCl (n = 2-7) clusters. From computed beta(vec) values, the hyperpolarizability has projection on the dipole moment vector for the superalkalis except the K2Cl and K5Cl. The absorption spectra point out that KnCl (n = 6-7) clusters can be suitable as a NLO material since they have transparency in the deep UV region (lambda< 300 nm).