Optical Absorption Energies of Molecular Defects in Pentaerythritol Tetranitrate Crystals: Quantum Chemical Modeling

The electronic structure and optical properties of a gas-phase PETN molecule, an ideal PETN crystal, and the crystal containing a series of common impurity defects (such as pentaerythrytol (PE), pentaerythrytol mononitrate (PEMonoN), pentaerythrytol dinitrate (PEDiN), pentaerythrytol trinitrate (PETriN), nitrite isomer of PETN (PETN–OONO), and trimethylolacetaldehyde trinitrate (TTriN)) were explored by means of quantum-chemical electronic structure calculations. We found that the molecular defects induce local electronic states in the band gap of PETN, and both HOMO and LUMO positions are sensitive to the presence of impurities. We predict how impurities affect the optical spectra of nitro-esters. We also establish that the crystal with molecular defects exhibits a range of excitation energies and hence allows for manipulation of the optical properties deliberately by various dopants or synthesis conditions.