Compression and the α-β Phase Transition of Plutonium

Abstract

Recent lifting of the security restrictions now permits publication of measurements of various effects of pressure on plutonium made during the war. Compressions on the alpha phase were measured at room temperature to 40 000 kg/cm² in one apparatus and to 100 000 in another. The total volume compression under 100 000 is very close to 10%. Compressibility decreases with increasing pressure as is normal. Exploration for other transitions was made to 20 000 kg/cm² at 100° and 200°—none were found. The pressure and the volume change of the alpha‐beta transition was measured at 162.6° and 205°. The transition curve is ``normal,'' the pressure rising with increasing temperature with downward curvature, and volume increment decreasing. The volume increment averages nearly 9%. The pressure of transition at 205° is very approximately 7000 kg/cm². The calculated latent heat of transition at the mean pressure is roughly 4.5 cal/g.