High Pressure X-ray Diffraction Studies on Barium

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Science  09 Aug 1963:
Vol. 141, Issue 3580, pp. 534-535
DOI: 10.1126/science.141.3580.534


Simultaneous x-ray diffraction and electrical resistance measurements on barium establish, with certainty, that Bridgman's 78-kb resistance transition is identical with his 59-kb volumetransition. During this transition, the bodycentered cubic structure changes to hexagonalclose packed. Lattice parameters for the latter structure at 62 kb (volume scale) are: a = 3.90 A, c = 6.15 A, and c/a = 1.58. Compression (AV/Vo) at 62 kb is 0.359 + 0.005 compared to 0.345 previously reported by Bridgman. Below the transition, at 49 kb, compression is 0.300 ± 0.005 compared to Bridgman's 0.288. Bridgman's 17-kb volume transition was not detected by x-ray diffraction.