Melting Point Prediction of Energetic Materials via Continuous Heating Simulation on Solid-to-Liquid Phase Transition

Abstract

Melting point is a significant property of energetic materials especially for melting cast explosives. Theoretical prediction of melting point is greatly meaningful for design and screening of low-melting-point candidates for casting medium. Herein, the melting behavior of nitromethane (NM) at different heating velocities ranging from 1 to 0.02 K/ps was investigated via molecular dynamics simulation of solid-to-liquid phase transition as a case study. Simulation results indicate that stable solid-to-liquid phase transition can occur when the heating velocity is less than or equal to 0.1 K/ps. The melting point of NM was predicted to be around 254 K, which is in reasonable agreement with the experimental value of 245 K. In the melting process, the structural transition from ordered arrangement to disordered distribution of NM molecules was observed as a result of the weakening of intermolecular interactions, leading to the decrease of C–H···O hydrogen bonds. The results reported here shed light on the important influence of heating velocity on accurate estimation of melting point in continuous heating simulations.

A Molecular Dynamics Study of Cyanate Ester Monomer Melt Properties

“…The procedure to simulate the solid–liquid phase transition imitates the process of heating a crystalline solid from low temperature while tracking the change in volume of the system in tandem. To calculate T m from MD simulations, researchers have typically used the volume (or density) as a function of temperature [ 12 , 13 , 34 , 35 , 36 , 37 , 38 ]. Within this thermodynamic theory of melting, at the melting temperature (constant temperature and pressure), the solid–liquid equilibrium is defined as: where s represents solid properties and l indicates liquid properties.…”

“…The order parameter equals 1 when molecules have perfect alignment along the director, which signifies a crystalline lattice in the solid state. This value decreases as the system becomes disordered and approaches 0 when molecules have isotropic orientations with respect to the director, which indicates liquid-like behavior [ 37 , 42 ]. The procedure of the calculation consisted of running an annealing simulation below the T m ( T m − 50 K) and above the T m ( T m + 50 K).…”

Theoretical calculation of nitro‐1‐(2,4,6‐trinitrophenyl)‐1H‐azoles energetic compounds

“…And in recent years, the molecular dynamics (MD) simulation has been applied to investigate and predict T m (or glass transition temperature) of amorphous models [20][21][22]. An attempts was made to predict the melting point of the new energetic compounds using the MD method of reference [20].…”

Predicting Melt Curves of Energetic Materials Using Molecular Models

“…Experimental determination of solid-liquid coexistence can be challenging for a variety of reasons, which include overheating, chemical reactivity, sample purity, as well as difficulties associated with generating high pressure environments. By explicitly defining the crystalline structure and omitting reactive pathways, molecular modeling can overcome several of the obstacles encountered experimentally and has been used to determine the melting behavior for a variety of energetic materials [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. However, determining the solidliquid coexistence of a material using particle-based modeling itself can be challenging due to the supercooled and superheated metastable states encountered on the time and length scales that are typically accessible [21].…”