Efficient approach to the free energy of crystals via Monte Carlo simulations: Application to continuous and orientation-dependent potentials

We extend a recently proposed approach to determine the absolute free energy of crystalline phases [Phys. Rev. E 92, 022103 (2015)PLEEE81539-375510.1103/PhysRevE.92.022103] to systems with continuous and orientation-dependent potentials. The method is based on the Monte Carlo thermodynamic integration method, and it provides a general procedure to obtain a simple, analytical, and exact reference free energy, together with an easy and accurate thermodynamic coupling integral. The approach is free from the difficulties of the standard method based on the harmonic coupling potential. A comparative discussion of both approaches is provided.