Abstract

Isotopic Effects in Chair Graphane

Author(s): Kelvin James*

Graphane is a layered substance made up of hydrogenated graphene sheets with a C:H ratio of 1:1. We investigate isotopic effects in chair graphane characteristics, in which H atoms alternate in a chair like arrangement on both sides of the carbon layer. We employ path-integral molecular dynamics simulations to investigate the impact of nuclear quantum effects on material equilibrium variables. Using an effective tight-bonding potential, the finite-temperature characteristics of graphane are investigated in the range 50 K-1500 K as functions of the isotopic mass of the constituent atoms. Substituting 13C for 12C at low temperatures results in a fractional change of 2.6104 in C-C distance and 3.9104 in graphane layer area. When 2H is substituted for 1H, the C-H bond undergoes a higher fractional change of 5.7 103. By applying tensile (compressive) in-plane stress, the isotopic impact in C-C bond distance increases (decreases). These findings are explained using a quasi harmonic approximation for the vibrational modes. The similarities and contrasts with graphene's isotopic effects are examined.