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Quasi-Particle Electronic Structure of Pristine and Hydrogenated Graphene on Weakly Interacting Hexagonal Boron Nitride Substrates
Published in James E. Morris, Kris Iniewski, Graphene, Carbon Nanotubes, and Nanostructures, 2017
Neerav Kharche, Saroj K. Nayak
Heterostructures of graphene (or graphone) and hBN are modeled using the repeated-slab approach, where the slabs periodic in the xy plane are separated by a large enough vacuum region along the z direction so that their interaction with the periodic images is negligible. The electronic structure calculations are performed in the framework of first-principles DFT at the level of the local density approximation (LDA) as implemented in the ABINIT code [32]. The Troullier-Martins norm-conserving pseudopotentials and the Teter-Pade parametrization for the exchange correlation functional are used [33,34]. A large enough vacuum of 10 Å in the z direction is used to ensure negligible interaction between periodic images. The Brillouin zone is sampled using Monkhorst-Pack meshes [35] of different size, depending on the size of Quasi-Particle Electronic Structure of Pristine and Hydrogenated Graphene the unit cell: 18 × 18 × 1 for Bernal stacked graphene on hBN, 6 × 6 × 1 for misaligned graphene on hBN, and 18 × 18 × 1 for graphone. Wavefunctions are expanded in plane waves with an energy cutoff of 30 Ha. The quasi-particle corrections to the LDA band structure are calculated within the G0W0 approximation, and the screening is calculated using the plasmon-pole model [36]. The Coulomb cutoff technique proposed by Ismail-Beigi et al. is used to minimize the spurious interactions with periodic replicas of the system [37]. The convergence of GW band gap is carefully tested.
Pressure dependent structural, dynamical, mechanical and electronic properties of magnesium dicarbide
Published in Philosophical Magazine, 2023
HaiYing Wu, YaHong Chen, Zi Jiang Liu, XiangYu Han, PengFei Yin
In this work, all the calculations were performed using the first-principles pseudopotential plane wave method in the framework of the density functional theory within ABINIT package [23]. The norm-conserving pseudopotential [24,25] plane waves, together with the Perdew Burke Ernzerhof [26] generalised gradient approximation (GGA) [27] exchange-correlation functions, were employed. The plane waves cut-off energy was set at 1088 eV for all considered structures, and the Monkhorst-Pack scheme [28] k-point grid samplings were set at 6 × 6 × 5, 10 × 10 × 4, 7 × 7 × 6, 8 × 8 × 8, 4 × 7 × 2, 8 × 8 × 12, 5 × 8 × 9, 8 × 3 × 6, 6 × 10 × 5 and 13 × 13 × 8 for the P42/mnm, P6/mmm, P-6m2, I4/mmm, Pmn21, Pnnm, P-1, Cmcm, C2/m and P-3m1 structures, respectively. The valence electron configurations considered in calculations were including for C 2s22p2 and Mg 3s2. Relaxation of the lattice constants were performed using the Broyden–Fletcher–Goldfarb–Shanno algorithm [29]. The convergence parameters were: total energy tolerance 0.5 × 10−5 eV/atom, maximum force tolerance 0.01 eV/Å, maximum stress component 0.02 GPa and maximum displacement 0.5 × 10−3 Å. The lattice dynamics were investigated to calculate the force constants using the linear response method in the framework of harmonic approximation. The dynamical matrices were computed on a regular 4 × 4 × 4 q grid and used for interpolation to obtain bulk phonon dispersion. The visualisations of anisotropic mechanical properties were obtained by ELATE code [30].