Large negative linear compressibility of Ag3[Co(CN)6].

Journal article

Silver(I) hexacyanocobaltate(III), Ag(3)[Co(CN)(6)], shows a large negative linear compressibility (NLC, linear expansion under hydrostatic pressure) at ambient temperature at all pressures up to our experimental limit of 7.65(2) GPa. This behavior is qualitatively unaffected by a transition at 0.19 GPa to a new phase Ag(3)[Co(CN)(6)]-II, whose structure is reported here. The high-pressure phase also shows anisotropic thermal expansion with large uniaxial negative thermal expansion (NTE, expansion on cooling). In both phases, the NLC/NTE effect arises as the rapid compression/contraction of layers of silver atoms--weakly bound via argentophilic interactions--is translated via flexing of the covalent network lattice into an expansion along a perpendicular direction. It is proposed that framework materials that contract along a specific direction on heating while expanding macroscopically will, in general, also expand along the same direction under hydrostatic pressure while contracting macroscopically.

Authors: Goodwin, A; Keen, D; Tucker, MG

• Publication status: Published
• Journal: Proceedings of the National Academy of Sciences of the United States of America
• Volume: 105
• Issue: 48
• Pages: 18708-18713
• Publication date: 2008-12-01
• DOI: 10.1073/pnas.0804789105
• EISSN: 1091-6490
• ISSN: 0027-8424
• Language: English
• Keywords: Pressure; Compressive Strength; Molecular Structure; Temperature; Cyanides; Cobalt; Silver Compounds