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MM: Fachverband Metall- und Materialphysik
MM 45: Computational Materials Modelling - Low dimensional systems
MM 45.5: Vortrag
Mittwoch, 18. März 2020, 18:15–18:30, IFW B
Prediction of two-dimensional square-A2B (A=Cu, Ag, Au, and B=S, Se) auxetic semiconductors with ultra-high negative Poisson*s ratios and unusually low lattice thermal conductivities — •Xin Chen1, Duo Wang1, Xiaobiao Liu2, Linyang Li3, and Biplab Sanyal1 — 1Department of Physics and Astronomy, Uppsala University, Box 516, 751,20 Uppsala, Sweden — 2School of Sciences, Henan Agricultural University, Zhengzhou 450002, PR China — 3Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
Using evolutionary crystal structure search and density functional calculations, we have obtained two-dimensional (2D) structures of A2B (A=Cu, Ag, Au, and B=S, Se). Structural, electronic and mechanical properties of the global minimum single-layer A2B structures were studied in detail. These structures have two types of geometries (s(I) and s(II)) with square symmetry, and are named square-A2B (s-A2B or s(I/II)-A2B) in this paper. All of the s-A2B structures are semiconductors with direct bandgaps ranging from 1.09 eV to 2.60 eV. Due to the ionic bonding nature, 2D s-A2B structures have unusually low lattice thermal conductivities, down to 1.5 Wm*1K*1 at room temperature. Also, s-A2B structures have ultra-low Young*s moduli, which are lower than most previously reported 2D materials, showing their extraordinary flexibility. Moreover, under the application of strain along the diagonal direction, five of these structuers show in-plane negative Poisson*s ratio (NPR). In particular, the NPR of s(II)-Cu2S can reach up to -1.68, higher than other predicted auxetic materials.