title: Electrostatic potential for O-H-O in tetragonal ammonium dihydrogenphosphate.
abstract: NH4H2PO4, Mr = 115.03, tetragonal, I42d, a = 7.500 (1), c = 7.550 (2) A, V = 424.7 A3, Z = 4, D chi = 1.799 g cm-3, lambda(Cu K alpha) = 1.5418 A, mu = 49.08 cm-1, F(000) = 240, T = 298 K, R = 0.021 for 99 independent reflections. The O-H-O system with O...O distance 2.493 (3) A is described in terms of the H atom in a single site undergoing anisotropic thermal vibrations. Then the O...H distance is 1.31 (9) A, the O-H-O angle is 145 (8) degrees and the maximum mean-square amplitude of vibration for H is 1.1 (7) A2. However, the probability distribution function for the proton could well have a double peak as reported in isomorphous KH2PO4 from high-resolution neutron diffraction. The electrostatic potential well in which the H occurs has a minimum of -1.13 e A-1.
authors.affiliation: Department of Crystallography, University of Pittsburgh, PA 15260.
authors.forename: W T
authors.initials: WT
authors.lastname: Klooster
authors.forename: B M
authors.initials: BM
authors.lastname: Craven
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D004563:Electrochemistry; D006859:Hydrogen / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D010710:Phosphates; C024788:ammonium phosphate; D006859:Hydrogen; D010100:Oxygen