Effects of medium range order on propagon thermal conductivity in amorphous silicon

We discuss the dependence of the propagon contribution to thermal conductivity on the medium range order (MRO) in amorphous silicon. Three different amorphous structures with the same size of 3.28 nm were studied. Among these three structures, two structures were constructed with experimentally observed MRO [M. M. J. Treacy and K. B. Borisenko, Science 335, 950 (2012)], and the other structure is from continuous random network (CRN), which lacks MRO and thus represents a randomized amorphous structure [G. Barkema and N. Mousseau, Phys. Rev. B 62, 4985 (2000)]. Using the simulated fluctuation electron microscopy and dihedral angle distribution, we confirm that the first two structures contain MRO in the length scale of 10-20 A while the CRN structure does not. The transport of propagons in the MRO and CRN structures is compared using the dynamic structural factor calculation and normal mode decomposition of the molecular dynamics simulation data, showing noticeably longer lifetime of propagons in MRO structures than in the CRN structure. The propagon thermal conductivity in MRO structures is estimated to be 50% larger than that in the CRN structure. Published under license by AIP Publishing.