title: Effects of carbon vacancies on the structures, mechanical properties, and chemical bonding of zirconium carbides: a first-principles study.
abstract: Interstitial carbides are able to maintain structural stability even with a high concentration of carbon vacancies. This feature provides them with tunable properties through the design of carbon vacancies, and thus making it important to reveal how carbon vacancies affect their properties. In the present study, using first-principles, we have calculated the properties of a number of stable and metastable zirconium carbides ZrC1-x (x = 0 and 1/n, n = 2-8) which were predicted by the evolutionary algorithm USPEX. Effects of carbon vacancies on the structures, mechanical properties, and chemical bonding of these zirconium carbides were systematically investigated. The distribution of carbon vacancies has significant influence on mechanical properties, especially Pugh's ratio. Nonadjacent carbon vacancies enhance Pugh's ratio, while grouped carbon vacancies decrease Pugh's ratio. This is explained by the changes in strength of Zr-C and Zr-Zr bonding around differently distributed carbon vacancies. We further explored the mechanical properties of zirconium carbides with impurities (N and O) by inserting N and O atoms into the sites of carbon vacancies. The enhanced mechanical properties of zirconium carbides were found.
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
authors.forename: Congwei
authors.initials: C
authors.lastname: Xie
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Skolkovo Institute of Science and Technology, 3 Nobel street, Skolkovo 143025, Russia and Moscow Institute of Physics and Technology, 9 Institutskiy Lane, Dolgoprudny City, Moscow Region 141700, Russia and Department of Geosciences and Center for Materials by Design, Stony Brook University, Stony Brook, New York 11794, USA. artem.oganov@stonybrook.edu.
authors.forename: Artem R
authors.initials: AR
authors.lastname: Oganov
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
authors.forename: Duan
authors.initials: D
authors.lastname: Li
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
authors.forename: Tekalign Terfa
authors.initials: TT
authors.lastname: Debela
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
authors.forename: Ning
authors.initials: N
authors.lastname: Liu
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
authors.forename: Dong
authors.initials: D
authors.lastname: Dong
authors.affiliation: International Center for Materials Discovery, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China. xiecw1021@mail.nwpu.edu.cn and Science and Technology on Thermostructural Composite Materials Laboratory, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, P. R. China.
authors.forename: Qingfeng
authors.initials: Q
authors.lastname: Zeng