Rb2CaH4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. Rb(1) is bonded in a 9-coordinate geometry to four equivalent H(1) and five equivalent H(2) atoms. Ca(1) is bonded to two equivalent H(2) and four equivalent H(1) atoms to form corner-sharing CaH6 octahedra. The corner-sharing octahedra are not tilted. There are two inequivalent H sites. In the first H site, H(2) is bonded to five equivalent Rb(1) and one Ca(1) atom to form a mixture of distorted corner and edge-sharing HRb5Ca octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second H site, H(1) is bonded in a distorted linear geometry to four equivalent Rb(1) and two equivalent Ca(1) atoms.
Rb2CaH4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. Rb(1) is bonded in a 9-coordinate geometry to four equivalent H(1) and five equivalent H(2) atoms. All Rb(1)-H(1) bond lengths are 3.14 Å. There is one shorter (2.90 Å) and four longer (3.18 Å) Rb(1)-H(2) bond lengths. Ca(1) is bonded to two equivalent H(2) and four equivalent H(1) atoms to form corner-sharing CaH6 octahedra. The corner-sharing octahedra are not tilted. Both Ca(1)-H(2) bond lengths are 2.31 Å. All Ca(1)-H(1) bond lengths are 2.25 Å. There are two inequivalent H sites. In the first H site, H(2) is bonded to five equivalent Rb(1) and one Ca(1) atom to form a mixture of distorted corner and edge-sharing HRb5Ca octahedra. The corner-sharing octahedral tilt angles range from 0-5°. In the second H site, H(1) is bonded in a distorted linear geometry to four equivalent Rb(1) and two equivalent Ca(1) atoms.