First principles reactive simulation for equation of state prediction

Abstract

The high cost of density functional theory has hitherto limited the ab initio prediction of equation of state (EOS). In this article, we employ a combination of large scale computing, advanced simulation techniques, and smart data science strategies to provide an unprecedented, ab initio performance analysis of the high explosive pentaerythritol tetranitrate (PETN). Comparison to both experiment and thermochemical predictions reveals important quantitative limitations of DFT for EOS prediction, and thus the assessment high explosives. In particular, we find DFT predicts the energy of PETN detonation products to be systematically too high relative to the unreacted neat crystalline material, resulting in suppression of the detonation velocity, pressure, and temperature at the Chapman-Jouguet (CJ) state. The energetic bias can be partially accounted for by high level electronic structure calculations of the product molecules. We also demonstrate a modeling strategy for mapping chemical composition across a wide parameter space with limited numerical data, the results of which suggest additional molecular species to consider in thermochemical modeling.

First-Principles Simulations of CuCl in High-Temperature Water Vapor

“…More generally, our NMC-ML approach has great utility in chemically reactive systems where bond breaking and formation are important and large energy activation barriers are present. 77 ■ ASSOCIATED CONTENT * sı Supporting Information…”

“…48−50 Our specific implementation of cluster moves used the following procedure: (1) pick a random seed atom, (2) build a cluster of atoms from the seed via our choice of "bonded" distances", (3) randomly displace the cluster center-of-position, (4) randomly rotate the cluster about the center-of-position (COP) via the Euler angles, (5) reject the move if new bonds are formed at the proposed location to enforce super detailed balance. 77 Bonded distances were defined as the sum of the covalent radii for an atom pair plus a buffer distance of 0.02 Å. The maximum allowed COP translation was 6.0 Å, and the maximum angular update was 60°for each Euler angle.…”

“…A detailed description of the ML potential used in NMC-ML will be provided in a forthcoming communication. 77 2.3. Analysis Methods.…”