Comparative DFT study of vibrational, electronic, and optical properties of energetic alkali metal salts based on nitrogen‐rich 5‐aminotetrazole

Abstract

This article presents a thorough density functional theory based comparative study on nitrogen-rich 5-aminotetrazole alkali metal salts M 5-At (M = Li, K, Rb, Cs). The calculated structural parameters using plane-wave pseudopotential method are consistent with the experimental results. The computed vibrational frequencies at ambient pressure show that vibrational modes in high energy region are due the N H bond of NH 2 group. Pressure variation IR spectra of these materials show clear frequency shifts where Li 5-At shows an overall red shift below 900 cm −1 contrary to the blue shift seen in other materials in this range. The born effective charge values reveal the presence of strong covalency between N, H, and C atoms whereas an increased ionic nature is seen as the atomic number of metal atoms increases. Furthermore, we used full potential linear augmented plane wave (FP-LAPW) method for calculating electronic structure and optical properties with TB-mBJ potential which provides an enhanced band gap for all materials compared to standard GGA functional. Electronic structure calculation reveals that all the compounds are indirect band gap insulators with the exception of Li 5-At. The computed partial density of states show mixed ionic-covalent nature in metal-N/C bonds and covalent nature in N C bonds. In addition, we are also presenting the optical properties such as real and imaginary dielectric constant, absorption, refraction, reflection, loss spectrum as functions of photon energy. From the optical properties we can conclude that all the studied compounds are optically anisotropic in nature and are good absorbers in the ultraviolet (UV) region. K E Y W O R D S 5-aminotetrazole, alkali metal salts, electronic properties, optical properties, vibrational properties 1 | INTRODUCTION Use of high nitrogen based energetic materials toward replacement of perchlorate in pyrotechnics is a subject of interest in recent times. Various derivative of perchlorate's are used since last few decades due to their intrinsic stability, low cost, reactivity, hygroscopic nature, and large positive oxygen balance. [1] Perchlorate based materials are now classified as environmentally dangerous and human health hazards. [2] These materials are believed to contaminate groundwater and interfere with the production and regulation of thyroid hormones, toxic and carcinogenic. [3,4] Research toward the replacement of rooted energetic materials (i.e., KClO 4 , NH 4 ClO 4 , Pb[N 3 ] 2) with increased performance and lower sensitivity to physical stimuli is hard to achieve. Over last few decades, rapid process in development of

Insight into the Isoreticularity of Li-MOFs for the Design of Low-Density Solid and Quasi-Solid Electrolytes

“…We identified Li + ion diffusion pathways in the isoreticular Li-MOFs of Li-BDC and Li-NDC, but the pathway in Li-BPDC was unavailable due to the convergence issues in the structural energy minimizations. Density functional perturbation theory (DFPT) was employed for the phonon calculations with the matrix of Born effective charges (BEC), − which was used to generate vibration intensities for the system. Li + ion diffusion pathways in Li-MOFs were calculated with the climbing image nudged elastic band (CINEB) method. − To obtain the energy profiles, the geometry of the initial and final systems were optimized first for the energy minimization, starting from the DFT calculations.…”

Regulating the Thermal Stability and Energy of Fused-Ring Energetic Materials by Hydrazo Bridging and Hydrogen-Bonding Networks

“…The discovery of new energetic materials (EMs) is one of the growing topics in the field of materials science. − One of the long-term objectives in this field is how to design and synthesize new energetic compounds with high energy, good safety, and high thermal stability. − Recent advances have shown that conjugated skeletons, strong intramolecular hydrogen bonds, and π–π interactions, which are structural features of traditional heat-resistant and insensitive EMs such as 1,3,5-triamino-2,4,6-trinitro-benzene (TATB) and 2,6-diamino-3,5-dinitro-pyrazine-1-oxide (LLM-105), contribute to the low sensitivity and high thermal stability of EMs. − Besides, NN/N–N bonds and nitro groups can increase the density and positive heat of formation (Δ H f ) and lead to the high energy density of EMs such as 1,3,5-trinitro-2,4,6-trinitroaminobenzene (TNTNB), 1,5-diaminotetrazole-4N-oxide (SYX-9), and 2,2′-azo-bis­(5-azidotetrazole) . The group of Prof. Ganapathy Vaitheeswaran made some constructive investigations by using calculation methods based on well-known EMs such as ammonium dinitramide (ADN), potassium dinitramide (KDN), 5-aminotetrazole (5-AT), 3,3′-dinitro-5,5′-bis-1,2,4-triazole-1,1′-diolate (DNBTO), 4,4′-bis­(nitramino)­azofurazan (DNAF), and octanitrocubane (ONC), which also support the above rules. − Bicyclic azolo azines constitute a family of nitrogen-rich conjugated 5/6-fused rings that allow all of the above structural features in one molecule, making them popular building blocks to construct new low-sensitivity and high-energy materials. For example, several reported materials such as 4-amino-3,7,8-trinitropyrazolo-[5,1- c ]­[1,2,4]­triazine ( I , PTX, Figure a), , 4-amino-3,7-dinitrotriazolo-[5,1- c ]­[1,2,4]­triazine ( II , DPX-26 or TTX), , and 6,8-diamino-7-nitrotetrazolo-[1,5- b ]­pyridazine ( III ) have shown a good balance between energy and safety.…”

Splicing oxygen-rich multidentate ligands and characteristic metals to construct flame colorants: abundant structures and attractive colors

“…6 Its performance can be adjusted by selecting constituent ions or independently modifying cation and anion components. [7][8][9] Therefore, energetic salts attract a lot of attention in the development of novel energetic materials. [10][11][12][13] The main parameter for evaluating the performance of energetic compounds is their oxygen balance.…”

“…6 Its performance can be adjusted by selecting constituent ions or independently modifying cation and anion components. 7–9 Therefore, energetic salts attract a lot of attention in the development of novel energetic materials. 10–13…”