Vibrational Properties and Structure of Pentaerythritol Tetranitrate

Abstract

Geometry optimizations and normal-mode analyses of the pentaerythritol tetranitrate (PETN) conformer belonging to the S 4 molecular point group and comprising the crystalline solid were performed using density functional theory methods (B3LYP and B3PW91). The basis sets used in this study were 6-31G(d) and 6-311+G(d,p). The structural results are in good agreement with experimental X-ray diffraction data. The predicted bond lengths and bond angles are accurate to within ∼2.5% and ∼1.2%, respectively. Raman and infrared spectra of crystalline PETN were measured and compared with the calculated spectra. The calculated and measured spectra agree very well in the spectral region below 1100 cm -1 ; the agreement is satisfactory for frequencies higher than 1100 cm -1 . On the basis of the calculations and analyses, normal mode assignments were made and mode symmetries determined.

First-principles intermolecular binding energies in organic molecular crystals

“…Three levels of interaction in OMCs have been identified [1]: electronic, intramolecular and intermolecular. The relatively strong intramolecular binding is responsible for the fact that vibrational frequencies for the isolated molecule (calculated, for example, with the Gaussian98 program) compare reasonably well with those in experiments using crystals, for example, PETN [2] (although, of course, the lattice modes cannot be calculated this way). In this case, the agreement between theory and experiment for these high-frequency vibrational modes supports the idea that the properties of the molecule are more-or-less unaffected by the presence of the lattice.…”

ReaxFF reactive molecular dynamics on silicon pentaerythritol tetranitrate crystal validates the mechanism for the colossal sensitivity

“…4,40 Experimental and DFT calculations also predicted that the PETN molecule has S 4 symmetry in the crystalline phase under ambient conditions. 13,14 PETN has been found experimentally to have three crystalline phases 5,40,41 where the most stable PETN-I has crystal symmetry P42 1 c with two formula units per unit cell. 41 The crystal structure data for Si-PETN are unavailable experimentally due to its extreme instability.…”

The Low-Temperature Vibrational Behavior of Pentaerythritol Tetranitrate

“…At atmospheric pressure, below the melting temperature of 141.3 °C (1), PETN appears as white crystals assembled into a tetragonal structure (P-42 1 c) with four molecules per unit cell arranged in an S 4 molecular symmetry. Both infrared (6,8,9) and Raman (9-10) characterizations of this phase exist, and several theoretical calculations of the vibrational frequencies of the crystal have been reported (8)(9)(10)(11)(12)(13). The mechanical properties of PETN at ambient conditions are quite interesting, as PETN exhibits a strong directional dependence to shock-initiated detonation (5,(14)(15)(16)(17)(18)(19)(20)(21)(22).…”