13th International Conference on Fracture June 16–21, 2013, Beijing, China -6- 4. Conclusions We have used MD and the re-parameterized Tersoff potential to model the porous structures of silica aerogels. We demonstrate that this potential is suitable for modeling thermal properties in amorphous silica. Using a quenching and expanding process, different densities of aerogel samples are generated. Good fits with previous results are obtained when the fractal dimensions are analyzed. Through RNEMD, their thermal conductivity is determined and the power-law fit of our data corresponds well with experimental studies. Thermal conductivities are also consistently higher than experimental bulk aerogel and analysis of the pore size distribution shows limited pore sizes could be the key issue here. Acknowledgements This work is supported by the Agency for Science, Technology and Research (A*STAR), Republic of Singapore. The authors thank the staff in A*STAR Computational Resource Centre for providing valuable technical support. ZS and JC are also grateful for the support from the National Natural Science Foundation of China through grant number 11242011 and number 11021202. References [1] S.S. Kistler, Coherent expanded aerogels and jellies. Nature, 127 (1931) 741-741. [2] J. Fricke, SiO2-Aerogels - Modifications and Applications. J Non-Cryst Solids, 121 (1990) 188-192. [3] N. Hüsing,U. Schubert, Aerogels - Airy Materials: Chemistry, Structure, and Properties. Angewandte Chemie - International Edition, 37 (1998) 22-45. [4] J. Fricke, Aerogels - Highly Tenuous Solids with Fascinating Properties. J Non-Cryst Solids, 100 (1988) 169-173. [5] L.D. Gelb, Simulation and Modeling of Aerogels Using Atomistic and Mesoscale Methods, in: M.A. Aegerter, N. Leventis, and M.M. Koebel (Eds.), Aerogels Handbook, Springer, New York, 2011, pp. 565-581. [6] T.Y. Ng, J.J. Yeo, Z.S. Liu, A molecular dynamics study of the thermal conductivity of nanoporous silica aerogel, obtained through negative pressure rupturing. J Non-Cryst Solids, 358 (2012) 1350-1355. [7] J. Kieffer,C.A. Angell, Generation of Fractal Structures by Negative-Pressure Rupturing of SiO2 Glass. J Non-Cryst Solids, 106 (1988) 336-342. [8] A. Nakano, L.S. Bi, R.K. Kalia, P. Vashishta, Molecular-Dynamics Study of the Structural Correlation of Porous Silica with Use of a Parallel Computer. Phys Rev B, 49 (1994) 9441-9452. [9] J.S.R. Murillo, M.E. Bachlechner, F.A. Campo, E.J. Barbero, Structure and mechanical properties of silica aerogels and xerogels modeled by molecular dynamics simulation. J Non-Cryst Solids, 356 (2010) 1325-1331. [10] B.W. van Beest, G.J. Kramer, R.A. van Santen, Force fields for silicas and aluminophosphates based on ab initio calculations. Phys Rev Lett, 64 (1990) 1955-1958. [11] G.J. Kramer, N.P. Farragher, B.W. van Beest, R.A. van Santen, Interatomic force fields for silicas, aluminophosphates, and zeolites: Derivation based on ab initio calculations. Phys Rev B Condens Matter, 43 (1991) 5068-5080. [12] S. Plimpton, Fast Parallel Algorithms for Short-Range Molecular-Dynamics. J Comput Phys, 117 (1995) 1-19. [13] J. Tersoff, Modeling solid-state chemistry: Interatomic potentials for multicomponent systems.
RkJQdWJsaXNoZXIy MjM0NDE=