Starting with the idea that wave mechanics should be useful in dealing with mechanical properties of solids, a connection between particle waves and deformation in crystals is developed. The connection is one in which Planck's constanthplays a prominent part. According to the view described, nonelastic deformation in crystals arises through the propagation of internally generated particle momentum waves with the de Broglie wavelength λ =h/mvi. Here,mandviare the mass and velocity, respectively, of certain, initially field‐free atoms that exist because of lattice defects in the crystal. The particle waves in question are not the probability waves of contemporary, orthodox quantum theory which satisfy the Schrödinger equation. Instead, real‐property waves governed by a new differential equation are proposed. Solutions to this equation for both finite and infinite lattices lead to frequency‐wave vector conditions from which a number of interesting results follow. These include the occurrence of characteristic frequencies or modes associated with nonelastic deformation, and, in particular, the existence of discrete audiofrequency modes whose frequencies depend on Planck's constant, atomic mass, and lattice segment length. The particle‐wave view thus leads directly to predictions of nonelastic audiofrequency resonances in vibration experiments and to expectations of acoustic emission during unidirectional plastic deformation. Applications of these same ideas to other aspects of mechanical behavior are also described briefly.