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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.46  No.6 (2005)  >  pp.1161-1166

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High-Pressure Elasticity and Auxetic Property of α-Cristobalite

Hajime Kimizuka1)2), Shigenobu Ogata1)3) and Yoji Shibutani1)3)
1) Department of Mechanical Engineering, Graduate School of Engineering, Osaka University
2) Engineering Technology Division, The Japan Research Institute, Limited
3) Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University

The structural variations with pressure in α-cristobalite, a low-density polymorph of SiO2, have been studied through first-principles calculations using the projector-augmented-wave (PAW) method, with particular emphasis on its elastic and auxetic properties. We provide theoretical ab initio results for the volume compressibility and a complete set of independent elastic constants of cristobalite under hydrostatic pressures up to 10–15 GPa. Our calculated structural and elastic properties under pressure are in good agreement with the experimental data. In addition, the corresponding results of the molecular-dynamics simulations with the interatomic potential are also presented for comparison. The dominant mechanism of compression is the reduction of the Si–O–Si angles within the α-cristobalite structure, whereas the SiO4 tetrahedron undergoes only a slight distortion. α-Cristobalite is more compressible than other SiO2 polymorphs as shown by their volume compressibilities, because of its characteristic framework structure similar to re-entrant honeycombs. With increasing pressure, the rotational motions of the rigid SiO4 tetrahedra play an important role in the compressive behavior of cristobalite. The present simulations confirm that the system undergoes transformation from auxetic to non-auxetic under hydrostatic pressure of ca. 2 GPa, while retaining strong elastic anisotropy.

negative Poisson’s ratio, auxetic materials, elastic constant, Birch-Murnaghan equation of state, density functional theory, molecular dynamics

Received: December 21, 2004
Accepted: February 17, 2005 , Published online: October 18, 2005
Copyright (c) 2005 The Japan Institute of Metals



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