Anomalous H[sbnd]C bond thermal contraction of the energetic nitromethane

Abstract

A systematic phonon spectrometric examination revealed that the HC phonon (2966 cm−1) undergoes blueshift under both compression and heating, but the CN (921 cm−1) and the NO (1403 cm−1) bonds undergo regular thermal redshift and compression blueshift in the Nitromethene (CH3NO2) assembly that is a solid under compression and a liquid under heating. An extension of the Grüneisen parameters integrates the phonon frequency shift to the intrinsic compressibility, thermal expansibility, specific heat, equilibrium bond length, atomic cohesive energy, and bonding energy density of the single bond which represents all of its sorts contributing to the spectral peak shift. The coupled hydrogen bond (HB, N (O):H–C), performs the same as the O:H–O of liquid water and ice I does in responding to heating. Results suggested that the combination of the N (O):H-C tension and the O:⇔:N repulsion stabilize the crystal structure and store energy, as they do in the cyclo-N5−:[4H3O+; 3H3O+ + 2NH4+] complexes.