Molecular modelling of the deformation mechanisms acting in auxetic silica

• Autorzy: Alderson A. , Alderson K. L. , Evans K. E. , Grima J. N. , Williams M. R. , Davies P. J.
• Języki publikacji: EN

Abstrakty

EN

Molecular mechanics simulations have been performed to undertake a systematic investigation into the structure and mechanical properties of alfa-cristobalite undergoing uniaxial loading along each of the 3 mutually orthogonal principal directions and also hydrostatic pressure loading. Simulations were performed using both the BKS and Burchart force-fields. The simulations indicate that pressure loading and uniaxial loading along the x3 direction leads to uniform variation of the four independent Si-O-Si intertetrahedral angles, indicative of cooperative tetrahedral rotation about tetrahedral axes which transform the alfa-cristobalite structure into the 'idealised' beat-cristobalite structure. Uniaxial loading along either of the transverse directions (x1; and x2) leads to a divergence of the intertetrahedral angles, consistent with tetrahedral rotation about the tetrahedral axes which transform the idealised beat-cristobalite structure into the "ordered' beta-cristobalite structure. The data also indicate that a phase transition to one of the proposed beta phases may be induced by a negative hydrostatic pressure or tensile stress along x3. The phase transition is accompanied by a change in sign of some of the Poisson's ratios (i.e. from positive to negative). A negative hydrostatic pressure is also predicted to lead to conversion of initially positive to negative Poisson's ratio values (within the same phase).

• Wydawca: Institute of Bioorganic Chemistry Scientific Publishers OWN, Polish Academy of Sciences
• Czasopismo: Computational Methods in Science and Technology
• Rocznik: 2004
• Tom: Vol. 10, nr 2
• Strony: 117--126
• Opis fizyczny: Bibliogr. 32 poz., rys.

Twórcy

autor

Alderson A.

• Centre for Materials Research and Innovation, Bolton Institute, Bolton BL3 5 AB, UK

autor

Alderson K. L.

• Centre for Materials Research and Innovation, Bolton Institute, Bolton BL3 5 AB, UK

autor

Evans K. E.

• Department of Engineering, University of Exeter, Exeter EX4 4QF, UK

autor

Grima J. N.

• Department of Chemistry, University of Malta, Msida MSD 06, Malta

autor

Williams M. R.

• Centre for Materials Research and Innovation, Bolton Institute, Bolton BL3 5 AB, UK

autor

Davies P. J.

• Centre for Materials Research and Innovation, Bolton Institute, Bolton BL3 5 AB, UK

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