Description:
<jats:title>Abstract</jats:title>
<jats:p> Normal coordinate analyses are reported for P<jats:sub>4</jats:sub>O<jats:sub>6</jats:sub> and P<jats:sub>4</jats:sub>O<jats:sub>10</jats:sub> . Harmonic force constants are given in terms of precisely defined symmetry coordinates. The force fields are used to calculate mean amplitudes of vibration, which are compared with electron diffraction data, and some discrepancies are discussed. Calculated atomic vibration mean-square amplitudes, which are of interest in crystallographic studies, are also given.</jats:p>