Abstract
Disordered systems are characterized by the absence of long-range structural order. This givesthem a high complexity in comparison to the corresponding cristalline structures and special physical and chemical properties involved in many applications. These complex systems are the subject of numerous theoretical and experimental studies ranging from the determination of their structure to functional properties. Several models and approaches have been developed to estimate the thermal conductivity in disordered materials (mostly based on classical molecular dynamics simulations) but the modeling is complicated and remains a challenge. In this study, we propose a model based on the Kubo formula involving harmonic eigenstates and phonons lifetimes calculation, and ab initio calculations. This requires first obtaining thermodynamically stable disordered structures for which it is possible to carry out the study of the thermal conductivity. In the framework of this study, amorphous silica is used as prototype of disordered structure.Ten models of amorphous silica containing 78 atoms have been generated by combining numerical simulations based on classical molecular dynamics using the BKS potential and density functional theory (DFT). The obtained structures show a dynamical stability (no imaginary phonon modes) after the determination of their vibration spectrum. The structural and dynamical properties investigated and averaged over a certain number of representative samples are in good agreement with experimental and theoretical data from the literature.After obtaining these representative structures, we developed a formulation of the thermal conductivity inspired by the Kubo and Allen-Feldman formalisms. This model has been implemented in a computer code and applied on the previously obtained silica samples and has given good results over a wide temperature range. These results are therefore promising to access the complex thermal properties of disordered materials using small numerical samples.