Nature of Interlayer Binding and Stacking of sp–sp ² Hybridized Carbon Layers: A Quantum Monte Carlo Study

Journal Article · 25 October 2017 · Journal of Chemical Theory and Computation

DOI: https://doi.org/10.1021/acs.jctc.7b00747 · OSTI ID:1395067

Shin, Hyeondeok  ^[1]; Kim, Jeongnim ^[2]; Lee, Hoonkyung ^[3]; Heinonen, Olle ^[4]; Benali, Anouar ^[1]; Kwon, Yongkyung ^[3]

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1. Argonne National Lab. (ANL), Argonne, IL (United States). Leadership Computing Facility
2. Intel Corporation, Hillsboro, OR (United States)
3. Konkuk Univ., Seoul (Korea). Dept. of Physics
4. Argonne National Lab. (ANL), Argonne, IL (United States). Material Science Division

α-graphyne is a two-dimensional sheet of sp-sp2 hybridized carbon atoms in a honeycomb lattice. While the geometrical structure is similar to that of graphene, the hybridized triple bonds give rise to electronic structure that is different from that of graphene. Similar to graphene, α-graphyne can be stacked in bilayers with two stable configurations, but the different stackings have very different electronic structures: one is predicted to have gapless parabolic bands and the other a tunable bandgap which is attractive for applications. In order to realize applications, it is crucial to understand which stacking is more stable. This is difficult to model, as the stability is a result of weak interlayer van der Waals interactions which are not well captured by density functional theory (DFT). We have used quantum Monte Carlo simulations that accurately include van der Waals interactions to calculate the interlayer binding energy of bilayer graphyne and to determine its most stable stacking mode. Our results show that inter-layer bindings of sp- and sp2-bonded carbon networks are significantly underestimated in a Kohn-Sham DFT approach, even with an exchange-correlation potential corrected to include, in some approximation, van der Waals interactions. Finally, our quantum Monte Carlo calculations reveal that the interlayer binding energy difference between the two stacking modes is only 0.9(4) eV/atom. From this we conclude that the two stable stacking modes of bilayer α-graphyne are almost degenerate with each other, and both will occur with about the same probability at room temperature unless there is a synthesis path that prefers one stacking over the other.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-06CH11357
• OSTI ID: 1395067
• Journal Information: Journal of Chemical Theory and Computation, Vol. 13, Issue 11; ISSN 1549-9618
• Publisher: American Chemical SocietyCopyright Statement
• Country of Publication: United States
• Language: English