On the influence of point defects on the structural and electronic properties of graphene-like sheets: a molecular simulation study

Abstract

The influence of vacancies and substitutional defects on the structural and electronic properties of graphene, graphene oxide, hexagonal boron nitride, and boron nitride oxide two-dimensional molecular models was studied using density functional theory (DFT) at the level of local density approximation (LDA). Bond length, dipole moment, HOMO-LUMO energy gap, and binding energy were calculated for each system with and without point defects. The results obtained indicate that the formation of a point defect does not necessary lead to structural instability; nevertheless, surface distortions and reconstruction processes were observed, mainly when a vacancy-type defect is generated. For graphene, it was found that incorporation of a point defect results in a semiconductor-semimetal transition and also increases notably its polar character. As with graphene, the formation of a point defect in a hexagonal boron nitride sheet reduces its energy gap, although its influence on the resulting dipole moment is not as dramatic as in graphene. The influence of point defects on the structural and electronic properties of graphene oxide and boron nitride oxide sheets were found to be mediated by the chemisorbed species.

Insertion of the Liquid Crystal 5CB into Monovacancy Graphene

“…point, occurs due to Jahn-Teller distortions in MV-G and is observed even without the presence of 5CB [57,58]. The small HOMO-LUMO energy gap is also consistent with values for MV-G [59]. The DOS exhibits symmetry in the spin states of the 5CB molecule (N, CN and CAR peaks), which means the molecule remains in a non-magnetic state with a DOS similar to that of 5CB on pristine graphene [38], while the MV-G itself is in a magnetic state.…”

Interplay between nanometer-scale strain variations and externally applied strain in graphene

“…The conclusions put forward below are identically derived for all widths, which is why we restrict the detailed presentation of the results below to the case of three times the interatomic carboncarbon distance. Preceding calculations suggest a maximum potential difference induced by point defects in hBN of the order of 100 meV [50][51][52]. We find this confirmed by our own DFT calculations for a nitrogen surface vacancy and a boron interstitial.…”

“…We therefore focus our analysis on applied tensile strain. As for the physical origin of the nanometer-scale strain variations in graphene, thermal fluctuations as well as frozen ripples from the fabrication process and atomic defects in substrates like hBN are conceivable [3,[47][48][49][50][51][52]; we consider both the effect of thermal fluctuations and of a static Gaussian potential to model defects in a hBN substrate. For both potential sources of nanometer-scale strain variations we observe an intriguing nonmonotonic variation of the average atomic displacements with increasing externally applied tensile strain.…”

On the Electronic Properties of the Boron Nitride Oxide by Density Functional Theory

“…First principles total energy calculations have been performed following the procedure reported in previous works [12][13][14][15][16][17][18][19][20][21][22]. We have applied the density functional theory (DFT) [23][24][25][26], developed by Kohn during the 1960 decade, as implemented in DMOL 3 quantum chemistry code [27][28][29].…”