Experimental and theoretical Compton profiles of calcium at room and high temperature

Isotropic Compton profiles of polycrystalline calcium in the f.c.c. (room temperature) and b.c.c. structure (525 degrees C) have been measured in situ with an Am-241 59.54 keV gamma-ray spectrometer. The band structure, electron momentum density and directional Compton profiles of Ca (b.c.c.) have been calculated and discussed by means of a self-consistent augmented-plane-wave method within the local-density approximation. A comparison of the experimental absolute Compton profiles with the theoretical calculations previously reported for the f.c.c. structure and the new ones for the b.c.c. structure exhibits a good quantitative agreement within 3 to 4% of the J(0) value. Experimental and theoretical differences between the Compton profiles in the two structures are within 1% and 0.5% of the J(0) value, indicating that the isotropic electron momentum density is relatively insensitive to this structural phase transition.