Size-dependent disproportionation (in ~ 2–20 nm regime) and hybrid Bond Valence derived interatomic potentials for BaTaO2N
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Interatomic potentials for complex materials (like ceramic systems) are important for realistic molecular dynamics (MD) simulations. Such simulations are relevant for understanding equilibrium, transport and dynamical properties of materials, especially in the nanoregime. Here we derive a hybrid interatomic potential (based on bond valence (BV) derived Morse and Coulomb terms), for modeling a complex ceramic, barium tantalum oxynitride (BaTaO2N). This material has been chosen due to its relevance for capacitive and photoactive applications. However, the material presents processing challenges such as the emergence of non-stoichiometric phases during processing, demonstrating complex processing–property correlations. This makes MD investigations of this material both scientifically and technologically relevant. The BV based hybrid potential presented here has been used for simulating sintering of BaTaO2N nanoparticles (~ 2–20 nm) under different conditions (using the relevant canonical ensemble). Notably, we show that sintering of particles of diameter < 10 nm requires no external sintering aids such as the addition of barium sources (since stoichiometry is preserved during heat treatment in this size regime). Also, we observe that sintering of particles > 10 nm in size results in the formation of a cluster of tantalum and oxygen atoms at the interface of the BaTaO2N particles. This is in agreement with the experimental reports. The results presented here suggest that the potential proposed can be used to explore dynamical properties of BaTaO2N and related systems. This work will also open avenues for development of nanoscience-enabled aid-free sintering approaches to this and related materials.
KeywordsMolecular dynamics Sintering Bond valence based interatomic potential Barium tantalum oxynitride Nano-interfacial phases
Kousika gratefully acknowledges the support from the HTRA fellowship. We thank the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras. We would like to thank IIT Madras for financial support through the project MET1415832NFIGTIJU. We acknowledge the P.G. Senapathy Center for computing resource, IIT Madras for the high-performance computing resources provided. We would also like to thank the Department of Science and Technology of the Government of India for supporting us (via Project nos. DST FILE NO. YSS/2015/001712 and DST 11-IFA-PH-07).
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Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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