1. Ferroelasticity Bratkovsky et al., 1996

2. Background Set As T approaches the transition temperature, the shear modulus goes to zero and the material loses strength.

3. Salje, 2000 Characteristic hysteresis of ferroelastic materials

4. Yamada et al., 1992 Spontaneous strain due to phase transitions

5. Yamada et al., 1992 Two possible phase transitions which lead to the twin patterns of ferroelastic materials

6. Nakayama et al., 1985 Extinction angles of two domains in a ferroelastic crystal

7. Bratkovsky et al., 1996 Tweed texture common in ferroelastic phase transitions

8. Salje, 2000 Evolution of domain structures with time

9. Salje, 2000 X-ray diffraction pattern for a twin wall

10. Mathematical Description of the Ferroelastic Material using Landau Theory Locherer et al., 1996

11. Chrosch et al., 1999 Bismayer et al., 1997 Experimental results compared with theory

12. Applications Ferroelastic materials could be useful for nanotechnology. The behavior of natural minerals could be greatly influenced by their ferroelastic microstructures.

13. Nanotechnology Aird et al., 1998

14. Geologic Impacts Salje et al., 1998

15. Conclusions The domain walls formed during ferroelastic phase transitions exhibit much different properties than the domains that they separate. The properties of domains and their walls could be very useful in mineral physics and mineralogy research.

16. References Aird, A., and Salje, E.K.H., 1998, J. Phys.: condens. matter, 10, L377. Bismayer, U., Rower, R.W., Morgenroth, W., Guttler, B., 1997, Solid State Ionics, 101-103, 585. Bratkovsky, A.M., Heine, V., Salje, E.K.H., 1996, Phil. Trans. R. Soc. Lond. A., 354, 2875. Chrosch, J., and Salje E.K.H., 1999, J. Appl. Phys., 85, 722. Locherer, K., Hayward, S., Hirst, P., Chrosch, J., Yeadon, M., Abell, J.S., and Salje, E.K.H., 1996, Phil. Trans. R. Soc. Lond. A., 354, 2815. Nakayama, H., Ishii, K., Chijiwa, E., Wada, M., Sawada, A., 1985, Solid State Commun., 55, 59. Salje, E.K.H., Gustaaf Van Tendeloo, A.B., Ishibashi, Y., Buckley, A., Nord, G.L., 1998, Am. Min, 83, 811. Salje, E.K.H., 2000, Contemp. Phys., 41, 79. Yamada, Y., and Uesu, Y., 1992, Solid State Commun., 81, 777.

17. Phase Transitions in Ferroelastic and Co-elastic Crystals By E. K. Salje, Andrew Putnis, Robert C. Liebermann, Michael F. Hochella Jr Thank You