Ab Initio Crystal Structure Prediction of the Energetic Materials LLM-105, RDX, and HMX.

Autor:	O'Connor D; Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States., Bier I; Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States., Tom R; Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States., Hiszpanski AM; Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States., Steele BA; Materials Science Division, Lawrence Livermore National Laboratory, Livermore, California 94550, United States., Marom N; Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.; Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.; Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
Jazyk:	angličtina
Zdroj:	Crystal growth & design [Cryst Growth Des] 2023 Aug 17; Vol. 23 (9), pp. 6275-6289. Date of Electronic Publication: 2023 Aug 17 (Print Publication: 2023).
DOI:	10.1021/acs.cgd.3c00027
Abstrakt:	Crystal structure prediction (CSP) is performed for the energetic materials (EMs) LLM-105 and α-RDX, as well as the α and β conformational polymorphs of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), using the genetic algorithm (GA) code, GAtor, and its associated random structure generator, Genarris. Genarris and GAtor successfully generate the experimental structures of all targets. GAtor's symmetric crossover scheme, where the space group symmetries of parent structures are treated as genes inherited by offspring, is found to be particularly effective. However, conducting several GA runs with different settings is still important for achieving diverse samplings of the potential energy surface. For LLM-105 and α-RDX, the experimental structure is ranked as the most stable, with all of the dispersion-inclusive density functional theory (DFT) methods used here. For HMX, the α form was persistently ranked as more stable than the β form, in contrast to experimental observations, even when correcting for vibrational contributions and thermal expansion. This may be attributed to insufficient accuracy of dispersion-inclusive DFT methods or to kinetic effects not considered here. In general, the ranking of some putative structures is found to be sensitive to the choice of the DFT functional and the dispersion method. For LLM-105, GAtor generates a putative structure with a layered packing motif, which is desirable thanks to its correlation with low sensitivity. Our results demonstrate that CSP is a useful tool for studying the ubiquitous polymorphism of EMs and shows promise of becoming an integral part of the EM development pipeline. Competing Interests: The authors declare no competing financial interest. (© 2023 The Authors. Published by American Chemical Society.)
Databáze:	MEDLINE
Externí odkaz:	Zobrazit plný text záznamu