文档介绍：CHAPTER 2 Theory of Solids Because of the difference in motion of the marble in these two cases, the mass of the particle would appear to be different in water than in oil. (As with many analogies, we must be careful not to betoo literal.) If we consider the movement ofan electron in the top of the valence band,we find that the effective mass is negative. An electron moving near the top ofan allowed band behaves as if it has a negative mass. We must keep in mind that the effective mass parameter is used to relate quantum mechanics and classical mechanics. The attempt to relate these two theories leads to this strange result ofa negative effective mass. However, solutions to Schrodinger's wave equation also lead to results that contradict classical mechanics (see results from Appendix E). The negative effective mass is another such example. In discussing the concept of effective mass in this section, we used an analogyof marbles moving through two liquids. Now consider placing an ice cube in the center ofa container filled with water: the ice cube will move upward toward the surface ina direction opposite to the gravitational force. The ice cube appears to have a negative effective mass since its acceleration is opposite to the external force. The effective mass parameter takes into account all internal forces acting on the particle. If we again consider an electron near the top