Solid State Ionics, Vol.308, 139-148, 2017
Crystal structure, charge distribution and vibrational study of strontium monohydrogen (SrHAsO4)
Crystals of a strontium monohydrogen arsenate were synthesized by hydrothermal method. The crystal structure of SrHAsO4 was re-investigated from single crystal X-ray data and by Charge-Distribution (CHARDI) investigation. The crystal is triclinic, space group P (1) over bar, a = 7.361(1) angstrom, b = 7.067(1) angstrom, c = 7.466(1) angstrom; alpha = 95.32(2)degrees, beta = 104.76(2)degrees, gamma = 88.11(3)degrees; Z = 4 and V = 373.93(2) angstrom(3), the refinement converged to R1 = 0.026 and wR2 = 0.074 for 1315 reflections with (I) > 2sigma(I). The crystal structure consists of protonated arsenate tetrahedra and SrOn polyhedra (n = 7, 8). The arsenate tetrahedra are assembled in centrosymmetric tetramers via strong O(1)-H(1)center dot center dot center dot O(5) (2.561 angstrom) and O(8)-H(6)center dot center dot center dot O(8)(i) (2.509 angstrom) hydrogen bonds. Each tetramer forms a short linear chain. The disordered model hydrogen atoms are performed mainly by Charge-Distribution (CHARDI) analysis. The structural model is validated by both bond-valence-sum (BVS) and charge-distribution methods (CHARDI). Infrared and Raman spectra of the title compound have been investigated at room temperature. An assignment of bands due to internal modes is proposed. The A-B-C profile observed in the infrared spectrum confirms the presence of strong hydrogen bonds.