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Title: Crystal structure of Pb{sub 2}V{sub 3}O{sub 9}: Rietveld refinement and electron lone-pair localization. The magnetic susceptibility of Sr{sup 2+}-substituted phases

Abstract

Powder neutron and X-ray diffraction data from Pb{sub 2}V{sub 3}O{sub 9} were collected and used for structure refinement. The triclinic lattice parameters from neutron data are reported. The nonstandard unit cell was chosen for comparison with the monoclinic structure of Sr{sub 2}V{sub 3}O{sub 9} with which it is nearly isostructural. The 6s{sup 2} electrons of PB{sup 2+} cause the lowering of the symmetry and distort the cooperative arrangement of the vanadyl bonds existing in the V-O framework of Sr{sub 2}V{sub 3}P{sub 9}. One of the two crystallographically independent Pb{sup 2+} is in a distorted, capped, octahedral environment formed by seven oxygen atoms with Pb-O bonds. The other Pb{sup 2+} is surrounded by nine oxygen atoms that form a distorted, tricapped, trigonal prism with Pb-O. The lone-pair 6s{sup 2} electrons were located and are about 0.58 {angstrom} from the nucleus. Of the four crystallographically independent vanadium atoms, two are in tetrahedral coordination with a mean oxidation number +5. The other two are in octahedral coordination with oxidation number +4. The octahedra link by corner sharing into an infinite chain parallel to [101]. The tetrahedra share corners with the octahedra to form two-dimensional sheets that are then joined by the Pb ionsmore » into a three-dimensional structure. One octahedral V{sup 4+} cation shows displacement from its polyhedral center toward an oxygen that is corner-shared in the octahedral chain, giving rise to a short vanadyl bond, 1.67(4) {angstrom}, and a long bond of 2.18(4) {angstrom}. The main difference between the lead and strontium vanadate framework is in the displacement of the second V{sup 4+} ion toward an oxygen that is corner-shared with a tetrahedron. Here the short bond length is 1.72(8) {angstrom} while it is 2.21(7) {angstrom} to the opposite apex. Thus, the cooperative displacement of the V{double{underscore}bond}O bond in the Sr{sub 2}V{sub 3}O{sub 9} chains is broken by the triclinic transformation, leading to a more disordered V{sup 4+} arrangement. This is the main reason for the observed differences in the magnetic susceptibilities of the Pb{sup 2+} and Sr{sup 2+} phases. An alternating J{sub 1} - J{sub 2} chain model was satisfactorily fitted for Pb{sub 2}V{sub 3}O{sub 9} while a regular chain model matched the data for Sr{sub 2}V{sub 3}O{sub 9}.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. des Sciences et Tech. de Lille, Villeneuve d'Ascq (FR)
OSTI Identifier:
20001167
Resource Type:
Journal Article
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 11; Journal Issue: 9; Other Information: PBD: Sep 1999; Journal ID: ISSN 0897-4756
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; VANADIUM OXIDES; LEAD OXIDES; TRICLINIC LATTICES; MAGNETIC SUSCEPTIBILITY; STRONTIUM OXIDES

Citation Formats

Mentre, O., Dhaussy, A.C., Abraham, F., Suard, E., and Steinfink, H. Crystal structure of Pb{sub 2}V{sub 3}O{sub 9}: Rietveld refinement and electron lone-pair localization. The magnetic susceptibility of Sr{sup 2+}-substituted phases. United States: N. p., 1999. Web. doi:10.1021/cm990073l.
Mentre, O., Dhaussy, A.C., Abraham, F., Suard, E., & Steinfink, H. Crystal structure of Pb{sub 2}V{sub 3}O{sub 9}: Rietveld refinement and electron lone-pair localization. The magnetic susceptibility of Sr{sup 2+}-substituted phases. United States. doi:10.1021/cm990073l.
Mentre, O., Dhaussy, A.C., Abraham, F., Suard, E., and Steinfink, H. Wed . "Crystal structure of Pb{sub 2}V{sub 3}O{sub 9}: Rietveld refinement and electron lone-pair localization. The magnetic susceptibility of Sr{sup 2+}-substituted phases". United States. doi:10.1021/cm990073l.
@article{osti_20001167,
title = {Crystal structure of Pb{sub 2}V{sub 3}O{sub 9}: Rietveld refinement and electron lone-pair localization. The magnetic susceptibility of Sr{sup 2+}-substituted phases},
author = {Mentre, O. and Dhaussy, A.C. and Abraham, F. and Suard, E. and Steinfink, H.},
abstractNote = {Powder neutron and X-ray diffraction data from Pb{sub 2}V{sub 3}O{sub 9} were collected and used for structure refinement. The triclinic lattice parameters from neutron data are reported. The nonstandard unit cell was chosen for comparison with the monoclinic structure of Sr{sub 2}V{sub 3}O{sub 9} with which it is nearly isostructural. The 6s{sup 2} electrons of PB{sup 2+} cause the lowering of the symmetry and distort the cooperative arrangement of the vanadyl bonds existing in the V-O framework of Sr{sub 2}V{sub 3}P{sub 9}. One of the two crystallographically independent Pb{sup 2+} is in a distorted, capped, octahedral environment formed by seven oxygen atoms with Pb-O bonds. The other Pb{sup 2+} is surrounded by nine oxygen atoms that form a distorted, tricapped, trigonal prism with Pb-O. The lone-pair 6s{sup 2} electrons were located and are about 0.58 {angstrom} from the nucleus. Of the four crystallographically independent vanadium atoms, two are in tetrahedral coordination with a mean oxidation number +5. The other two are in octahedral coordination with oxidation number +4. The octahedra link by corner sharing into an infinite chain parallel to [101]. The tetrahedra share corners with the octahedra to form two-dimensional sheets that are then joined by the Pb ions into a three-dimensional structure. One octahedral V{sup 4+} cation shows displacement from its polyhedral center toward an oxygen that is corner-shared in the octahedral chain, giving rise to a short vanadyl bond, 1.67(4) {angstrom}, and a long bond of 2.18(4) {angstrom}. The main difference between the lead and strontium vanadate framework is in the displacement of the second V{sup 4+} ion toward an oxygen that is corner-shared with a tetrahedron. Here the short bond length is 1.72(8) {angstrom} while it is 2.21(7) {angstrom} to the opposite apex. Thus, the cooperative displacement of the V{double{underscore}bond}O bond in the Sr{sub 2}V{sub 3}O{sub 9} chains is broken by the triclinic transformation, leading to a more disordered V{sup 4+} arrangement. This is the main reason for the observed differences in the magnetic susceptibilities of the Pb{sup 2+} and Sr{sup 2+} phases. An alternating J{sub 1} - J{sub 2} chain model was satisfactorily fitted for Pb{sub 2}V{sub 3}O{sub 9} while a regular chain model matched the data for Sr{sub 2}V{sub 3}O{sub 9}.},
doi = {10.1021/cm990073l},
journal = {Chemistry of Materials},
issn = {0897-4756},
number = 9,
volume = 11,
place = {United States},
year = {1999},
month = {9}
}