Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 54: 2D Materials II: Growth

O 54.7: Vortrag

Mittwoch, 9. März 2016, 12:00–12:15, S053

Prediction of metastable two-dimensional compounds in the C/Si system using global optimization techniques, and investigation of their electronic properties — •Johann Christian Schön and Rico Gutzler — MPI for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart

We employ the global energy landscape exploration package G42+[1,2] to predict (meta)stable two-dimensional crystalline polymorphs in the carbon/silicon system for a range of compositions: C:Si = 1:0, 3:1, 2:1, 1:1, 1:2, 1:3, and 0:1.[1] During the global search (energy function: DFT), both atom positions and cell parameters in the xy-plane were allowed to vary freely. The global optimization method used was basin-hopping-simulated annealing, with two consecutive local optimizations - the first keeping the atoms restricted to the z = 0 plane, while the second one also permitted relaxation in the z-direction. For all compositions, the lowest energy 2D-structures exhibited a graphene-like super-structure with 6-membered rings, but many quite stable competing minimum structures containing a variety of rings of size 4 - 12 were also observed. Deviations from planarity occurred most frequently for structures where a high local concentration of the Si-atoms was present. Complementing geometric structure prediction, we performed band-structure calculations to investigate the effect of geometry and C:Si ratio on the electronic properties of these 2D-materials.

[1] J. C. Schön, Proc. Appl. Ceram. 9:157-168 (2015); [2] J. C. Schön, G42+ Manual, www.chemie.uni-bonn.de/ac/schoen/forschung/g42-manual, (2015)