Theoretical Studies of Solid Nitromethane

Abstract

A classical potential to simulate the dynamics of a nitromethane crystal as a function of temperature and pressure is described. The intramolecular part of the potential was taken as superposition of bond stretching, bond bending, and torsional angles terms. These terms were parametrized on the basis of the geometric and spectroscopic (vibrational frequencies and eigenvectors) data obtained using ab initio molecular orbital calculations performed at the B3LYP/6-31G* level on an isolated molecule. The intermolecular potential used is of the Buckingham 6-exp form plus charge−charge Coulombic interactions and has been previously developed by us (Sorescu, D. C.; Rice, B. M.; Thompson, D. L. J. Phys. Chem. 1997, B101, 798) to simulate crystals containing nitramine molecules and several other classes of nitro compounds. The analyses performed using constant pressure and temperature molecular dynamics simulations and molecular packing calculations indicate that the proposed potential model is able to reproduce accurately the changes of the structural crystallographic parameters as functions of temperature or pressure for the entire range of values investigated. In addition, the calculated bulk modulus of nitromethane was found in excellent agreement with the corresponding experimental results. Moreover, it was determined that the present potential predicts correctly an experimentally observed 45° change in methyl group orientation in the high-pressure regime relative to the low-temperature configuration. The analysis of the linear expansion coefficients and linear compression data indicate anisotropic behavior for the unit cell edges.

Molecular Packing and Molecular Dynamics Study of the Transferability of a Generalized Nitramine Intermolecular Potential to Non-Nitramine Crystals

“…We found that the potential predicts the right order of stability for different phases of HNIW (e > ß > y) crystals in agreement with experimental measurements. 4 At 300 K, the average lattice dimensions agree very well with experimental values, with the corresponding differences for the individual cell edge lengths being no more than 1.0% for the e-polymorph, 0.9% for the /5-polymorph, and 2.5% for the y-polymorph. For the <=-and /-phases, the variations of the unit cell angle ß from the experimental values are 1.3% and 0.1%, respectively, while the other two angles of the unit cell remain approximately equal to 90°.…”

“…The recently developed explosive 2,4,6,8,10, can be described as a bridged pair of RDX molecules, suggesting that the intermolecular forces for HNTW might be similar to those of RDX. To explore this possibility, we performed MP and NPT-MD simulations 2 for three of the polymorphs of HNIW (ß-, e-, and y-phases) at ambient pressure and over the temperature range 4.2 to 425 K using the form of potential used in the RDX study.…”

“…4 The crystals are composed of monocyclic, polycyclic, and acyclic nitamine molecules. The molecules associated with the nitramine crystals were chosen as representative examples of acyclic and cyclic nitramines.…”

A DFT study on structural, vibrational properties, and quasiparticle band structure of solid nitromethane

“…A considerable amount of theoretical work has been performed using classical and quantum molecular dynamics simulations under various conditions. 11,12,[18][19][20] By using classical interatomic potential molecular dynamics simulations, Sorescu et al 11 predicted the structural properties of nitromethane crystals. The thermal decomposition of nitromethane was investigated using Car-Parrinello molecular dynamics simulations, which reveals that it undergoes a thermal decomposition at 2200 K with the cleavage of the C-N bonds.…”

Shock response of single crystal and nanocrystalline pentaerythritol tetranitrate: Implications to hotspot formation in energetic materials

“…5-10 a) wuha@ustc.edu.cn b) sluo@pims.ac.cn Theoretical or simulation studies on condensed-phase energetic materials employ such techniques as static electronic structure, [11][12][13][14] molecular dynamics (MD) simulations using empirical or electronic-structure-based force fields, [15][16][17] as well as reactive force fields (ReaxFF), 18,19 and ones based on coarse-grained (CG), particle-based methods. [20][21][22][23] The energetic materials explored include nitromethane, 11,15,16,[24][25][26][27][28][29] octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), [30][31][32][33][34] hexa-hydro-1,3,5-trinitro-1,3,5-triazine (RDX), 18,[35][36][37][38][39][40][41][42] 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 12,13 and pentaerythritol tetranitrate (PETN), 23 among others. 14 See Rice and Sewell 43 for a recent review on this subject.…”