Atom Structure Models

Crystal structures of two metals A and B are two-dimensional square lattices with same lattice constant a. Electrons in metals behave as free electrons. The Fermi surfaces corresponding to A and B are shown by solid circles in figures.

The electron concentrations in A and B are and , respectively. The value of is:

The mean distance between the two atoms of an HD molecule is , where H and D denote hydrogen and deuterium, respectively. The mass of the hydrogen atom is . The energy difference between the two lowest lying rotational states of HD in multiples of is: