Molecular dynamics simulation of the effects of swift heavy ion irradiation on multilayer graphene and diamond-like carbon

Abstract

As a promising material used in accelerators and in space in the future, it is important to study the property and structural changes of graphene and diamond-like carbon on the surface as a protective layer before and after swift heavy ion irradiation, although this layer could have a loose structure due to the intrinsic sp 2 surrounding environment of graphene during its deposition period. In this study, by utilizing inelastic thermal spike model and molecular dynamics, we simulated swift heavy ion irradiation and examined the track radius in the vertical direction, as well as temperature, density, and sp 3 fraction distribution along the radius from the irradiation center at different time after irradiation. The temperature in the irradiation center can reach over 11000 K at the beginning of irradiation while there would be a low density and sp 3 fraction area left in the central region after 100 ps. Ring analysis also demonstrated a more chaotic cylindrical region in the center after irradiation. After comprehensive consideration, diamond-like carbon deposited by 70 eV carbon bombardment provided the best protection.

Speed-Dependent Adaptive Partitioning QM/MM for Displacement Damage Simulations

“…For such 'single-pass' AP-QM/MM methods, 58,68 corrections to the transition forces and the SDEM are unavailable and difficult to develop. Since most DD simulations are done in the NVE ensemble, [4][5][6][7][8][9][10][11][12][13][14][15] neglecting the SDEM is inapplicable as well. I therefore do not apply corrections to the SDEM for the SDAC simulations in this paper.…”

“…The 2 outermost layers of atoms are fixed, 4,7,9,10 and the next 4 layers of atoms are Langevin thermostated 92 at 300K following the setup in literature. [4][5][6][7][8][9][10][11][12][13][14][15] This allows the excess energy introduced to the system by the PKA to dissipate in order to simulate the DD generation. The initial kinetic energy of the PKA is set to 0.5 keV, and the initial direction of the PKA is the same as in Sec.…”

Speed-Dependent Adaptive Partitioning QM/MM for Displacement Damage Simulations

“…I develop the SDAC method by extending the AC method to allow speed-dependent criterion, so as to carry out QM/MM simulations of the DD generation in solids. Such simulations are carried out in the NVE ensemble with temperature controlling layers, [4][5][6][7][8][9][10][11][12][13][14][15] so I only discuss NVE simulations in the following. A speed-dependent ξ results in a PES that depends on both the atomic positions and the speeds, and the Newton's second law EOM no longer applies.…”

“…For such 'single-pass' AP-QM/MM methods, 58,68 corrections to the transition forces and the SDEM are unavailable and difficult to develop. Since most DD simulations are done in the NVE ensemble, [4][5][6][7][8][9][10][11][12][13][14][15] neglecting the SDEM is inapplicable as well. I therefore do not apply corrections to the SDEM for the SDAC simulations in this paper.…”

“…The 2 outermost layers of atoms are fixed, 4,7,9,10 and the next 4 layers of atoms are Langevin thermostated 92 at 300K following the setup in literature. [4][5][6][7][8][9][10][11][12][13][14][15] This allows the excess energy introduced to the system by the PKA to dissipate in order to simulate the DD generation. The initial kinetic energy of the PKA is set to 0.5 keV, and the initial direction of the PKA is the same as in Sec.…”