Synthesis and single crystal structures of ternary phosphides Li4SrP2 and AAeP (A = Li, Na; Ae = Sr, Ba)

摘要

Two new (NaSrP, Li4SrP2) and two known (LiSrP, LiBaP) ternary phosphides have been synthesized and characterized using single crystal X-ray diffraction studies. NaSrP crystallizes in the non-centrosymmetric hexagonal space group P62m (# 189, a = 7.6357(3) angstrom, c = 4.4698(3) angstrom, V = 225.69(2) angstrom(3), Z = 3, and R/wR = 0.0173/0.0268). NaSrP adopts an ordered Fe2P structure type. PSr6 trigonal prisms share trigonal (pinacoid) faces to form 1D chains. Those chains define large channels along the [001] direction through edge-sharing. The channels are filled by chains of PNa6 face-sharing trigonal prisms. Li4SrP2 crystallizes in the rhombohedral space group R3m (# 166, a = 4.2813(2) angstrom, c = 23.437(2) angstrom, V= 372.04(4) angstrom(3), Z = 3, and R/wR = 0.0142/0.0222). In contrast to previous reports, LiSrP and LiBaP crystallize in the centrosymmetric hexagonal space group P6(3)/mmc (# 194, a = 4.3674(3) angstrom, c = 7.9802(11) angstrom, V = 131.82(2) angstrom(3), Z = 2, and R/wR = 0.0099/0.0217 for LiSrP; a = 4.5003(2) angstrom, = 8.6049(7) angstrom, V = 150.92(2) angstrom(3), Z = 2, and R/wR = 0.0098/0.0210 for LiBaP). Li4SrP2, LiSrP, and LiBaP can be described as Li3P derivatives. Li atoms and P atoms make a graphite-like hexagonal layer, (2)(infinity)[LiP](2-). In LiSrP and LiBaP, Sr or Ba atoms reside between (2)(infinity)[LiP](2-) layers to substitute for two Li atoms of Li3P, while in Li4SrP2, Sr substitutes only between every other (2)(infinity)[LiP](2-) layer. (c) 2006 Elsevier Inc. All rights reserved.