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An Overview of Crystal Chemistry Study on Thermal Expansion of Minerals

LI Suo-zai, LIAO Li-bing   

  1. China University of Geosciences, Beijing 100083
  • Received:2000-06-20 Revised:2000-06-20 Online:2000-06-20 Published:2000-06-20

Abstract: Thermal expansion is one of the important properties of m inerals and o f theoretical and practical significance. This paper is a review of the crystal chemistry studies on mineral thermal expansion. With some examples, the correlat ions between the thermal expansion coefficients of minerals and the types of cr ystal structures, the nature of chemical bonds, the valencies of ions , the interionic distances, the percentage ionic characters, the electronic conf igurations of ions and the chemical compositions are discussed and summarised . The crystal chemistry approach has been used in the calculation of the th ermal expansion coefficients for minerals with simple structures and composition s. Models suitable for calculation of the thermal expansion coefficients for m inerals with complex structures and compositions are to be developed. To calculate the thermal expansion coefficients of minerals in a wide range, the minerals should be classified according to their crystal chemistry properties. In the light of framework structures upon heatig during which the polyhedra are tilted or fixed, the thermal expansion properties can be divided into two catego ries, the bond-length expansion caterory and the structures with tilts category . The transition metal cation compounds should be considered separately. Based on the above-mentioned types, for the bond-length expansion category only the expansion of bonds in the framework should be considered, but for the structur e with tilts category both the expansion of bonds and the tilts of the polyhedra in framework should be considered.