Abstract
The electronic surroundings of phosphorus and lithium atoms in the ionic conductor lithium dihydrogen phosphate (LDP) have been studied by single-crystal nuclear magnetic resonance (NMR) spectroscopy at room temperature. From orientation-dependent NMR spectra of a large homegrown LDP single crystal, the full 31P chemical shift (CS) and 7Li quadrupole coupling (QC) tensor was determined, using a global fit over three rotation patterns. The resulting CS tensor is characterized by its three eigenvalues: δ 11 P A S = ( 67.0 ± 0.6 ) ppm, δ 22 P A S = ( 13.9 ± 1.5 ) ppm, and δ 33 P A S = ( − 78.7 ± 0.9 ) ppm. All eigenvalues have also been verified by magic-angle spinning NMR on a polycrystalline sample, using Herzfeld–Berger analysis of the rotational side band pattern. The resulting 7Li QC tensor is characterized by its quadrupolar coupling constant χ = Q 33 P A S = ( − 71 ± 1 ) kHz and the two eigenvalues Q 11 P A S = ( 22.3 ± 0.9 ) kHz, and Q 22 P A S = ( 48.4 ± 0.8 ) kHz. The initially unknown orientation of the mounted crystal, expressed by the orientation of the rotation axis in the orthorhombic crystal frame, was included in the global data fit as well, thus obtaining it from NMR data only.
Highlights
Lithium dihydrogen phosphate (LDP), LiH2 PO4, exhibits a conductivity of the order of 10−4 Ω−1 cm−1, which is exceptionally high for a solid at room temperature
Not much attention has been paid to the electronic surroundings of the phosphorus and lithium atoms, which despite their light mass have been found to be quite immobile in the crystal structure at room temperature [6]
Since relatively large single crystals of lithium dihydrogen phosphate (LDP) with several mm in diameter can be grown from aqueous solution [7], a good method to analyze the local surroundings of these nuclei is Nuclear Magnetic Resonance (NMR) of single crystals
Summary
Lithium dihydrogen phosphate (LDP), LiH2 PO4 , exhibits a conductivity of the order of 10−4 Ω−1 cm−1 , which is exceptionally high for a solid at room temperature. This conductivity is predominantly attributed to fast proton movements in the crystal lattice of LDP [1]. 2b,atoms are tetrahedrally and the phosphorus (purple) bothbond tetrahedrally coordinated oxygen (red).c The coordinated by each atoms other with one Al-N directed parallel to the by crystallographic axis.hydrogen (c) Individual, atoms (ivory) stabilize the crystal structure by forming hydrogen bonds structure (dotted lines) between the the PO4three tetrahedrally coordinated, aluminum and nitrogen atom in the crystal of AlN, in which and. Equal, 4shorter, bonds Al/N—I/II/III [1.8891(8) Å] and the longer bond Al/N—IV [1.9029(16) Å] along the three-fold rotation axis are highlighted. a Drawing generated with the Vesta program [11]
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