Abstract
Calcium disilicide (CaSi2) possesses a layered structure composed of alternating monolayers of silicene (MLSi) and calcium. Here the mechanism by which fluorine (F) diffusion into CaSi2 leads to a phase transformation from MLSi to bilayer silicene (BLSi) was investigated. Disorder in intra-layer atomic arrangements and F aggregation were observed using HAADF-STEM in areas of low F concentration. Transformation of MLSi to BLSi in CaSi2Fx was predicted to occur at x = 0.63 based on cluster expansion (CE) and density functional theory (DFT) analyses, and these results agreed well with HAADF-STEM observations. The occurrence of F aggregation at low concentrations was also confirmed by Monte Carlo simulations using the interaction parameters obtained in CE analysis. Bader charge analysis, DFT calculations of charged states, and ab initio molecular dynamics simulations indicated that the aggregated F atoms withdrew electrons from MLSi, destabilizing the buckled honeycomb structure of MLSi in CaSi2. This charge imbalance caused the transformation of MLSi to the covalent-like BLSi.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
