The origin of diverse lattice dynamics in the graphene family

We employ first principles based density functional theory calculations to explore the lattice dynamics of members of the graphene family. We explore the changes observed in the lattice thermal conductivity via adopting physical models for estimating phonon lifetimes. This allows us to establish a connection between the parameters such as group velocity, Grüneisen parameter, and Debye temperature of the acoustic phonon modes and the lattice thermal conductivity. Our calculations show that the presence of buckling reduces the group velocity and the Debye temperature of the sheets down the group, and hence, reduces their lattice thermal conductivity. However, there is no linear dependence between the buckling height and the observed lowering. An increase in buckling height in sheets with different geometries of the same atomic species, beyond a certain limit, does not lead to change in the group velocity and the Debye temperature of the sheets.