LATTICE VIBRATION-SPECTRA .78. INFRARED AND RAMAN STUDIES ON CALCIUM, ZINC AND CADMIUM HYDROXIDE HALIDES CA(O(H,D))CL, CD(O(H,D))CL, ZN(O(H,D))F AND BETA-ZN(O(H,D))CL

IR and Raman spectra of Zn(OH)F, beta-Zn(OH)Cl and isostructural Ca(OH)Cl and Cd(OH)Cl and of deuterated specimens recorded at ambient and liquid nitrogen temperature are presented and assigned to OH(OD) stretching, librational and translational modes. The spectra obtained are discussed on the basis of the layered crystal structures of these hydroxide halides. The main results are (i) detection and proof of the presence of very weak hydrogen bonds in the case of M(OH)Cl (M = Ca, Cd) and for OH(2) of Zn(OH)F [in addition to ordinary hydrogen bonds in the case of beta-Zn(OH)Cl and OH(1) of Zn(OH)F] with OH stretching wavenumbers of the corresponding hydroxide ions partially greater than that of free, gaseous OH- ions, (ii) a less symmetrical structure of Ca(OH)Cl and Cd(OH)Cl compared with that obtained from the heavy atoms alone and (iii) proof of the presence of two different kinds of hydroxide ions in nearly equal amounts in Zn(OH)F containing two lattice sites each occupied by F- and OH-. The high-energy shift of the OH modes mentioned above is attributed to the synergetic effect.