Efficient Calculation of Lattice Thermal Conductivity by Molecular Dynamics Simulation: Role of Isobaric-Isothermal Relaxation and Potential Cutoff Distance

This work studied the Green-Kubo approach of calculating thermal conductivity with molecular dynamics (MD) simulation. In MD lattice thermal conductivity calculation, zero-pressure volume relaxation in the isobaric-isothermal (NPT) ensemble which determines lattice parameters, is often not included in standard procedure. Several MD simulations of fcc-based structures with different lattice parameters were performed to calculate lattice thermal conductivity and phonon density of states. The results were compared to experimental references and ab initio datas to suggest that NPT relaxation is crucial for accurate thermal conductivity calculation. Moreover, dependency between potential cutoff and lattice thermal conductivity in MD simulation was also studied. The results suggested that lattice thermal conductivity is not strictly dependent on potential cutoff distance, but exactly function of lattice parameters given by NPT relaxation. We concluded that properly reducing the cutoff distance can greatly improve computation cost of thermal conductivity calculation without sacrificing the accuracy.