New ReaxFF Potential for Modeling SiCO Ceramics

Reference	Presenter	Authors (Institution)	Abstract
18-030	Peter Kroll	Kroll, P.(UT Arlington);	Amorphous silicon oxycarbide (a-SiCO) ceramic materials provide a wide range of applications. They are used as membranes for gas separation, radiation-tolerant materials, thermal barrier coatings, and anode materials in Li-ion batteries. To enable accurate large-scale atomistic simulations of SiCO, we develop a new reactive force field – ReaxFF – that promises DFT-accuracy at significantly lower computational costs. Unfortunately, current parameterizations of ReaxFF for interaction between the elements Si, C, and O have significant flaws. They neither match enthalpy differences nor kinetic stability at high temperature of ab-initio MD simulations. Most importantly, however, none of the current ReaxFF parameter sets replicates an amorphous SiCO glass phase, which has been subject of many experimental studies. We develop new ReaxFF parameters using a library of DFT-computed data. The library includes not only observed SiO2 and SiC structures, but also more than 10,000 hypothetical crystalline SiCO structures. Moreover, it comprises over 1,000 models of amorphous SiCO with variety of geometries and bonds. Based on this “Big Data”, new force fields for SiCO show correspondence between ReaxFF and DFT energies. Moreover, the amorphous SiCO glass phase is reproduced and remains kinetically stable up to temperatures as observed in experiment.
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