Structural evolution of in-plane hybrid graphene/hexagonal boron nitride heterostructure upon heating

HTT Nguyen, JOURNAL OF MOLECULAR GRAPHICS & MODELLING, 125, 108579 (2023).

DOI: 10.1016/j.jmgm.2023.108579

In-plane hybrid graphene/hexagonal boron nitride (h-BN) heterostructure (graphene/hBN/graphene) is studied via molecular dynamics simulation. The initial configuration (6400-atom graphene/6200-atom h-BN/6400-atom graphene) is heated up from 50 K to 7500 K via Tersoff potential. To study the structural evolution, some thermal dynamics quantities are calculated such as the coordination number, the total energy per atom, the heat capacity, the angular distribution, and the distribution of rings. Some main results are calculated and presented as follows: i) The sudden increase of total energy per atom at the melting point (5500 K) exhibits the first order phase transition from the crystalline state to a liquid state of the hybrid graphene/h-BN/graphene heterostructure; ii) The heat capacity shows two peaks. The first peak (at 5500 K) represents the phase transition from the crystalline to a liquid states while the second one (at 6300 K) represents the formation of gaseous atoms of B and N in the hBN sheet; iii) The coordination number of three decreases dramatically at temperature of 5500 K (about 10% lefts for each type of atoms) leading to the formation of the first peak in the graph of the heat capacity. The coordination number of zero for B and N in the h-BN layer increases significantly (over 55%) at 6300 K causing the formation of the second peak in the graph of the heat capacity; iv) The influence of the relative number of atoms of h-BN to graphene in the hybrid graphene/h-BN/graphene heterostructure on the structural evolution upon heating is considered as follows. The number of atoms in the graphene sheets remains constant (6400 atoms per sheet) while the one of the h-BN sheet varies in size (780, 1560, 3120, 4680, 5490, 5880, 6080, and 6200 atoms). The results show that although the phase transition is still the first order type, the phase transition temperature decreases as the size of the h-BN layer in the hybrid heterostructure increases.

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