The effects that limit deuterium-deuterium (D-D) fusion in bound systems, as opposed to those limiting D-D fusion in free space, are the result of quantum-mechanical particle-particle wave function correlation, which may inhibit wave function overlap. Whether or not this occurs at room temperature is determined by system energy minimization, not Gamow theory. A counterintuitive example, known from atomic physics, that demonstrates how this alternative criterion may alter the relevant quantum mechanics is illustrated by the helium atom. At room temperature, near-complete overlap of the two helium electrons takes place when energy is minimized, while Gamow theory predicts negligible overlap. On the other hand, energy minimization does predict that no nucleus-nucleus overlap ever occurs in any normal molecule. In D+ ion band-state matter, D+-D+ overlap occurs if the distributed charge view of quantum reality is correct, in which case D+ band-state matter converts to 4He++ band-state matter, releasing heat throughout a crystal lattice. This occurs in the limit x → 1 in PdDx (in agreement with experiments), provided adequate crystalline order is present. Further deuterium loading requires that additional injected deuterium occupy ionic band-like states in which only a small fraction of each additional deuterium atom occupies a lattice unit cell. Then, in each nuclear reaction, again to minimize energy of the entire system, the energy is distributed over many lattice sites, inhibiting production of energetic particles. Theory shows that steady-state power is proportional to the loading current. These points are discussed. An expression for P is derived, and possible cold fusion reactions are summarized.