Indeed, for solid metallic chemical elements at room temperature, atom-molar heat capacities range from about 2.8 R to 3.4 R. Large exceptions at the lower end involve solids composed of relatively low-mass, tightly bonded atoms, such as beryllium (2.0 R, only of 66% of the theoretical value), and diamond (0.735 R, only 24%). Those conditions imply larger quantum vibrational energy spacing, thus many vibrational modes are "frozen out" at room temperature. Water ice close to the melting point, too, has an anomalously low heat capacity per atom (1.5 R, only 50% of the theoretical value).