{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T15:17:45Z","timestamp":1785424665908,"version":"3.56.0"},"reference-count":0,"publisher":"International Union of Crystallography (IUCr)","issue":"1","license":[{"start":{"date-parts":[[2026,2,1]],"date-time":"2026-02-01T00:00:00Z","timestamp":1769904000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/legalcode"},{"start":{"date-parts":[[2026,2,1]],"date-time":"2026-02-01T00:00:00Z","timestamp":1769904000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/legalcode"}],"content-domain":{"domain":["iucr.org","wiley.com","iucrj.org"],"crossmark-restriction":true},"short-container-title":["Acta Crystallogr B Struct Sci Cryst Eng Mater","Acta Crystallogr B","Acta Crystallogr B Struct Sci","Acta Cryst B","Acta Cryst B Struct Sci Cryst Eng Mater","Acta Cryst Sect B","Acta Cryst Sect B Struct Sci Cryst Eng Mater","Acta Crystallogr Sect B","Acta Crystallogr Sect B Struct Sci Cryst Eng Mater","Acta Crystallogr Sect B Struct Sci"],"accepted":{"date-parts":[[2025,12,3]]},"published-print":{"date-parts":[[2026,2,1]]},"abstract":"<jats:p>\n                    Single crystals of lacunary apatite structure-type compound Pb\n                    <jats:sub>4<\/jats:sub>\n                    Na(PO\n                    <jats:sub>4<\/jats:sub>\n                    )\n                    <jats:sub>3<\/jats:sub>\n                    were prepared with a flux\/solid-state-reaction technique and consecutive melt-growth to examine spatial distribution and stereochemical activity of the 6\n                    <jats:italic>s<\/jats:italic>\n                    <jats:sup>2<\/jats:sup>\n                    lone electron pair of Pb\n                    <jats:sup>2+<\/jats:sup>\n                    using X-ray diffraction. The target compound crystallized in space group\n                    <jats:italic>P<\/jats:italic>\n                    6\n                    <jats:sub>3<\/jats:sub>\n                    \/\n                    <jats:italic>m<\/jats:italic>\n                    with unit-cell edge lengths\n                    <jats:italic>a<\/jats:italic>\n                    = 9.7345\u2005(12)\u2005\u00c5 and\n                    <jats:italic>c<\/jats:italic>\n                    = 7.2130\u2005(18)\u2005\u00c5 without any indication of configurational ordering of Pb\n                    <jats:sup>2+<\/jats:sup>\n                    and Na\n                    <jats:sup>+<\/jats:sup>\n                    at the crystallographic\n                    <jats:italic>A<\/jats:italic>\n                    1 site. The anion channel running through the structure was confirmed as vacant. Residual density attributable to the deformed 6\n                    <jats:italic>s<\/jats:italic>\n                    <jats:sup>2<\/jats:sup>\n                    electron cloud was found 0.6\u2005\u00c5 apart from the\n                    <jats:italic>A<\/jats:italic>\n                    2-site position on the\n                    <jats:italic>A<\/jats:italic>\n                    2 triangle normal to\n                    <jats:bold>c<\/jats:bold>\n                    . The lack of a channel-site anion induced shrinkage of the unit cell and the O3 trigonal antiprism in the\n                    <jats:italic>xy<\/jats:italic>\n                    plane, and an increase in the twist angle of the\n                    <jats:italic>A<\/jats:italic>\n                    1O\n                    <jats:sub>6<\/jats:sub>\n                    trigonal metaprism compensated for the shrinkage of the latter to keep the volume of the\n                    <jats:italic>A<\/jats:italic>\n                    1O\n                    <jats:sub>9<\/jats:sub>\n                    coordination polyhedron constant. Systematic comparison of the size of the\n                    <jats:italic>A<\/jats:italic>\n                    2 triangle in Pb\n                    <jats:sub>4<\/jats:sub>\n                    Na(PO\n                    <jats:sub>4<\/jats:sub>\n                    )\n                    <jats:sub>3<\/jats:sub>\n                    and other apatite-type compounds indicates no contribution from the 6\n                    <jats:italic>s<\/jats:italic>\n                    <jats:sup>2<\/jats:sup>\n                    electron orbital on the size of the\n                    <jats:italic>A<\/jats:italic>\n                    2 triangle and limited space-filling ability of the orbital.\n                    <jats:italic>A<\/jats:italic>\n                    2 cations are attached on the periphery of a large void formed by the in-plane distortion of the hexagonal close packed arrangement of (\n                    <jats:italic>B<\/jats:italic>\n                    O\n                    <jats:sub>4<\/jats:sub>\n                    )\n                    <jats:sup>3\u2212<\/jats:sup>\n                    complex anions. In other words, a face-sharing array of\n                    <jats:italic>A<\/jats:italic>\n                    2 octahedra was inserted `as a tube' through the framework. The sizes of\n                    <jats:italic>A<\/jats:italic>\n                    1O\n                    <jats:sub>9<\/jats:sub>\n                    and\n                    <jats:italic>B<\/jats:italic>\n                    O\n                    <jats:sub>4<\/jats:sub>\n                    polyhedra and their framework define the maximum size of the\n                    <jats:italic>A<\/jats:italic>\n                    2 triangle, while the triangle can easily be shrunk by attraction from an anion, such as F\n                    <jats:sup>\u2212<\/jats:sup>\n                    , in the channel.\n                  <\/jats:p>","DOI":"10.1107\/s2052520625010844","type":"journal-article","created":{"date-parts":[[2026,1,13]],"date-time":"2026-01-13T15:45:10Z","timestamp":1768319110000},"page":"68-77","update-policy":"https:\/\/doi.org\/10.1107\/cm_01","source":"Crossref","is-referenced-by-count":0,"title":["Spatial distribution of 6\n                    <i>s<\/i>\n                    <sup>2<\/sup>\n                    lone electron pair in Pb\n                    <sub>4<\/sub>\n                    Na(PO\n                    <sub>4<\/sub>\n                    )\n                    <sub>3<\/sub>\n                    and stereochemical activity of the 6\n                    <i>s<\/i>\n                    <sup>2<\/sup>\n                    electron cloud in lead-bearing apatites"],"prefix":"10.1107","volume":"82","author":[{"given":"Kotomi","family":"Hirano","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02hwp6a56","id-type":"ROR","asserted-by":"publisher"}],"department":["Division of Geosciences and Civil Engineering, Graduate School of Natural Science and Technology"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6324-2339","authenticated-orcid":true,"given":"Hiroki","family":"Okudera","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02hwp6a56","id-type":"ROR","asserted-by":"publisher"}],"department":["School of Geosciences and Civil Engineering, College of Science and Engineering"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"329","published-online":{"date-parts":[[2026,2,1]]},"container-title":["Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials"],"original-title":[],"link":[{"URL":"https:\/\/journals.iucr.org\/b\/issues\/2026\/01\/00\/ra5162\/ra5162.pdf","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.iucr.org\/b\/issues\/2026\/01\/00\/ra5162\/ra5162.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,3]],"date-time":"2026-02-03T14:09:04Z","timestamp":1770127744000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.iucr.org\/paper?S2052520625010844"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,1]]},"references-count":0,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,2]]}},"alternative-id":["S2052520625010844"],"URL":"https:\/\/doi.org\/10.1107\/s2052520625010844","relation":{"is-supplemented-by":[{"id-type":"doi","id":"10.1107\/S2052520625010844\/ra5162sup1.cif","asserted-by":"subject"},{"id-type":"doi","id":"10.1107\/S2052520625010844\/ra5162Isup2.hkl","asserted-by":"subject"}]},"ISSN":["2052-5206"],"issn-type":[{"value":"2052-5206","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,2,1]]},"assertion":[{"value":"Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials","order":0,"name":"journal","label":"Publication","explanation":{"URL":"https:\/\/journals.iucr.org\/b"},"group":{"name":"general","label":"General"}},{"value":"research papers","order":1,"name":"content_type","label":"Content type","explanation":{"URL":"https:\/\/journals.iucr.org\/b\/services\/notesforauthors.html"},"group":{"name":"general","label":"General"}},{"value":"Available","URL":"https:\/\/scripts.iucr.org\/cgi-bin\/citedin?ra5162","order":2,"name":"article_metrics","label":"Article metrics","group":{"name":"general","label":"General"}},{"value":"Yes","order":0,"name":"peer_reviewed","label":"Peer reviewed","group":{"name":"peer_review","label":"Peer review"}},{"value":"Single blind","order":1,"name":"review_process","label":"Review process","group":{"name":"peer_review","label":"Peer review"}},{"value":"12 September 2025","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication history"}},{"value":"3 December 2025","order":1,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication history"}},{"value":"1 February 2026","order":2,"name":"published_online","label":"Published online","group":{"name":"publication_history","label":"Publication history"}},{"value":"This article has supporting information","name":"supplementary_materials","label":"Supplementary materials","explanation":{"URL":"https:\/\/scripts.iucr.org\/cgi-bin\/sendsup?ra5162"}},{"value":"\u00a9 2026 Hirano & Okudera","order":0,"name":"copyright","label":"Copyright","explanation":{"URL":"https:\/\/journals.iucr.org\/services\/copyrightpolicy.html"},"group":{"name":"copyright_and_licencing","label":"Copyright and licencing"}},{"value":"Creative Commons Attribution (CC-BY)","order":1,"name":"license","label":"Licence","explanation":{"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/legalcode"},"group":{"name":"copyright_and_licencing","label":"Copyright and licencing"}}]}}