Schematic of the asymmetric pair potential giving rise to thermal expansion in a solid. Two potentials for two different binding energies (depths of minima) are shown (orange and cyan solid lines: potential for high and low binding energies, respectively). The dotted black lines show the slopes at the attractive parts of the potentials, which are smaller for lower binding energy. The dashed lines (orange, high binding energy; cyan, low binding energy) indicate the average location of the particle, which shifts to the right (larger interparticle distance) for higher temperature, leading to thermal expansion. For the deeper potential, the particle position is shown for two temperatures.
