Structure and thermal properties associated with some hydrogen bonds in crystals I. The isotope effect

A study of the vibrational spectrum is one method of investigating the forces between atoms in a crystal. Since the lattice vibrations influence the distance between crystal planes, information on crystal forces can also be obtained from X-ray measurements of the thermal expansion. Finally, in crystals containing hydrogen it is possible by substituting deuterium to make large changes in certain vibrational frequencies, without altering any other factor which determines crystal structure.