4. Conclusion
In summary, based on the structure of
Ti3AlC2, possible structures for layered
ordered double-transition metals MAX compound
Ti2ZrAlB2 have been searched by ab
initio calculations. One Ti3AlB2 and
two new Ti2ZrAlB2 structures have been
successfully designed. The calculations of formation enthalpy, phonons
and elastic constants all confirmed the phase stabilities of them. High
B/G ratios indicate that they are all good ductile materials. Study of
their mechanical properties show their Poisson ratios are larger than
0.25, which means ionic bonds dominate in these three crystal materials.
The electron localization functions have also demonstrated that the
ionic Ti-B and Zr-B bonding play a key role in their chemical
properties, but metal bonds also exist in the structures. Results of
electronic densities of states show that they all have good electrical
conductivity, and the conductivity are mainly contributed by Ti-d and
B-p electron orbitals for Ti3AlB2, and
Ti-d, Zr-d and B-p electron orbitals for two
Ti2ZrAlB2. Although the high temperature
resistance of these three MAX compounds in present study is not as good
as the MAX carbides, they also have not low melting points. In
particular, they also have good ductility. The unusual combination of
these properties of these compounds makes them promising candidates in
the field of engineering application. At the end of present wok, we also
explored the factors limiting its heat resistance, it is due to the weak
bonding between Al and the M(2)-B-M(1)-C-M(2) (M=Ti or Zr).
Funding Information: Project supported by the Scientific
Research Key Project Foundation of Henan Province (Grant No.
222102230081 and 202102210482), the Foundation of LCP (Laboratory of
Computational Physics) (Grant No. 6142A05210101) and the Youth Backbone
Project of Henan Province (No. 2019GGJS137).
ACKNOWLEDGMENTS: All the computational work is accomplished in
Henan Key Laboratory of Magnetoelectronic Information Functional
Materials, Zhengzhou University of Light Industry funded by the
Laboratory of Computational Physics and Henan Province.
AUTHOR CONTRIBUTIONS: Shiquan Feng: Funding acquisition;
writing–original draft. Feng Guo: Formal analysis; software;
writing–review and editing. Yongqiang Wang: Formal analysis; funding
acquisition. Chaosheng Yuan: Data curation; investigation. Xuerui Cheng:
Methodology; visualization. Feng Miao: Formal analysis, supervision.