Syntheses, Crystal Structures, and Thermal Analyses of Solvent-Free Ca(AlD 4 ) 2 and CaAlD5. -Solvent-free Ca(AlD4)2 and CaAlD5 are synthesized by mechanochemical milling of CaD2 and AlD3 in the molar ratios of 1:2 and 1:1, respectively, under a D2 gas pressure of 0.3 MPa. Their structures are determined by high-resolution synchrotron powder XRD, powder neutron diffraction, and Raman spectroscopy. Ca(AlD 4 ) 2 crystallizes in the orthorhombic space group Pbca with Z = 8 (Ca(BF 4 ) 2 -type structure). It releases 4.8 wt.% D2 at an onset temperature of 427 K. CaAlD5 crystallizes in the monoclinic space group P21/c with Z = 8 (α-SrAlF5-type structure) and releases 7.1 wt.% D2 at an onset temperature of 554 K.