1. Erice, 2009 Compression Systematics in Minerals Dr Robert T Downs Department of Geosciences University of Arizona Tucson, AZ

2. O, Fe, Mg, Si

3. The Earth represents a P,T,x diagram of Fe,Mg,Si,O on a grand scale.

4. Therefore, most of the material in the Earth, and perhaps in the Universe, exists at elevated pressure and temperature conditions.

5. Other reasons to study minerals at high-pressure Synthesis of new phases P&T

6. Peanut butter to diamonds with Kevin Righter, Lunar and Planetary Lab, U of Arizona

7. Other reasons to study minerals at high-pressure Synthesis of new phases Study of new properties Superconductor Hg-1223 Pressure (GPa) T C (K)

8. Other reasons to study minerals at high-pressure Synthesis of new phases Study of new properties Probe of interatomic forces 3 /z C (Å 3 /esu) K p -1 (Mbar -1 )

9. Apply Pressure to a Solid The volume of the solid must decrease. Thus the atoms must get closer together. My interest lies in understanding the various ways that the crystal structure can accommodate volume decrease.

10. Spinel structure e.g. Al 2 MgO 4

13. Spinel structure e.g. Al 2 MgO 4

14. Spinel structure e.g. Fe 2 FeO 4

15. Spinel structure e.g. Mg 2 SiO 4

16. quartz

19. cristobalite

21. Silica polymorphs

22. Compression Mechanisms 1.Bond compression 2.Angle bending 3.Combination of both

23. Pyroxene

32. Pyroxene Chemistry M2 M1 Si 2 O 6 jadeite NaAlSi 2 O 6 diopside CaMgSi 2 O 6 enstatite Mg 2 Si 2 O 6

33. Diopside

34. KTP (potassium titanyl phosphate)

35. KTP

36. Allan and Nelmes, 1996 KTP

40. Quantum calculation of Na-O bond formation

41. Diopside

42. Spodumene Arlt and Angel, 2000

45. jadeite

47. Kanoite, MnMgSi 2 O 6 Arlt & co-workers, 1997-2000

48. Images courtesy of Thilo Arlt

50. Bridgman’s Law: For isostructural materials, cell volumes at ambient conditions are inversely correlated with the bulk modulus. i.e. Larger the cell, the smaller the bulk modulus

52. Diopside

53. Sympathetic bonds Antipathetic bonds McCarthy et al, (2008)

54. Garnet

55. Compression Mechanisms 1.Bond compression 2.Angle bending 3.Combination of both 4.Bonding changes 5.Reconstructive phase changes

56. Reconstructive Phase Changes e.g. graphite to diamond e.g. albite to jadeite + quartz

57. MgO at pressure

60. NiAs structure, hcp analogue to rocksalt