The potential energy curve were symmetric figure

For each class of materials (metals, ceramics, and polymers), the greater the atomic bonding energy, the deeper and more narrow this potential energy trough. As a result, the increase in interatomic separation with a given rise in temperature will be lower, yielding a smaller value of � l. Table 17.1 lists the linear coefficients of thermal expansion for several materials. With regard to temperature dependence, the magnitude of the coefficient of expansion increases with rising temperature. The values in Table 17.1 are taken at room temperature unless indicated otherwise. A more comprehensive list of coefficients of thermal expansion is provided in Table B.6 of Appendix B.

Interatomic distance Interatomic distance 0 0

(a) (b)

FIGURE 17.3 (a) Plot of potential energy versus interatomic distance,
demonstrating the increase in interatomic separation with rising temperature. With heating, the interatomic separation increases from r0 to r1 to r2, and so on. (b) For a symmetric potential energy-versus-interatomic distance curve, there is no increase in interatomic separation with rising temperature (i.e., r1 � r2 � r3 ).