Structural Information
The crystal structure of calcium hexaboride is a cubic lattice with calcium at the cell centre and compact, regular octahedra of boron atoms linked at the vertices by B-B bonds to give a three-dimensional boron network. Each calcium has 24 nearest-neighbor boron atoms The calcium atoms are arranged in simple cubic packing so that there are holes between groups of eight calcium atoms situated at the vertices of a cube. The simple cubic structure is expanded by the introduction of the octahedral B6 groups and the structure is a CsCl-like packing of the calcium and hexaboride groups. Another way of describing calcium hexaboride is as having a metal and a B62- octahedral polymeric anions in a CsCl-type structure were the Calcium atoms occupy the Cs sites and the B6 octahedra in the Cl sites. The Ca-B bond length is 3.05 Å and the B-B bond length is 1.7 Å.
43Ca NMR data contains δpeak at -56.0 ppm and δiso at -41.3 ppm where δiso is taken as peak max +0.85 width, the negative shift is due to the high coordination number.
Raman Data: Calcium hexaboride has three Raman peaks at 754.3, 1121.8, and 1246.9 cm−1 due to the active modes A1g, Eg, and T2g respectively.
Observed Vibrational Frequencies cm−1 : 1270(strong) from A1g stretch, 1154 (med.) and 1125(shoulder) from Eg stretch, 526, 520, 485, and 470 from F1g rotation, 775 (strong) and 762 (shoulder) from F2g bend, 1125 (strong) and 1095 (weak)from F1u bend, 330 and 250 from F1u translation, and 880 (med.) and 779 from F2u bend.
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