Time-Domain Terahertz Spectroscopy and Density Functional Theory Studies of Nitro/Nitrogen-Rich Aryl-Tetrazole Derivatives

Abstract

The paper reports the time-domain THz spectroscopy studies of noncentrosymmetric energetic nitro/ nitrogen-rich aryl-tetrazole high-energy molecules. The fingerprint spectra in the THz domain reveal the role of different functional groups attached to position "1" of the tetrazole moiety, which controls the energetic properties. These responses are deliberated through density functional theory (DFT) calculations. The synthesized aryl-tetrazoles exhibit high positive heat of formation (369−744 kJ/mol), high detonation velocities, and pressures (D v : 7734−8298 m·s −1 ; D p : 24−28 GPa) in comparison to the noncentrosymmetric 2,4,6-trinitrotoluene (TNT). These compounds exhibit variation in the refractive indices and absorption between 0.1 and 2.2 THz range. The DFT studies at the molecular and single-crystal level (using plane wave pseudo potential method) endorse in detecting these bands (with ∼1% deviation). The calculated vibrational frequencies and linear optical properties are found to have good agreement with the experimental data in UV−visible and THz regions.

Cross-correlation technique for phase error correction in reflection mode terahertz time-domain spectroscopy

“…THz-TDS can either be performed in transmission mode or re ection mode. In transmission mode, the generated terahertz are allowed to pass through the sample, and the transmitted signal is detected on the other side [10]. But transmission setup has certain limitations, such as the sample is assumed to be optically transparent in the terahertz radiation; moreover, it is challenging to study thick or highly absorbing samples as they may attenuate the terahertz signal signi cantly.…”

Terahertz spectral investigation of temperature induced polymorphic transformation of 2,2dinitroethylene-1,1-diamine

“…14 For our purposes, terahertz time-domain spectroscopy (THz-TDS) is claimed to be a sensitive tool for investigating polymorphic transformations. Despite THz spectral features of numerous energetic materials, including traditional explosives 15,16 and new ionic salts, 17,18 being widely reported, methods to determine the characteristics of the polymorphic transformation process urgently need development.…”