TlF and PbO under High Pressure: Unexpected Persistence of the Stereochemically Active Electron Pair This work was supported by the Swedish National Science Research Council (NFR) and the Göran Gustafsson Foundation.

Even under a pressure of 46 GPa, the low-symmetry lone-pair structures of isoelectronic TIF and PbO (see picture for β-PbO), classic examples of systems with a stereochemically active lone pair, resist transformation into the corresponding high-symmetry NaCl and CsCl structures. Ab initio calculations allowed a simple bonding picture for lone-pair structures involving inert-pair elements to be developed.

[1]  J. Galy,et al.  Stéréochimie des eléments comportant des paires non liées: Ge (II), As (III), Se (IV), Br (V), Sn (II), Sb (III), Te (IV), I (V), Xe (VI), Tl (I), Pb (II), et Bi (III) (oxydes, fluorures et oxyfluorures) , 1974 .

[2]  R. Roy,et al.  High‐Pressure‐High‐Temperature Polymorphism of the Oxides of Lead , 1961 .

[3]  Georg Kresse,et al.  Norm-conserving and ultrasoft pseudopotentials for first-row and transition elements , 1994 .

[4]  G. Kresse,et al.  Ab initio molecular dynamics for liquid metals. , 1993 .

[5]  Blöchl,et al.  Improved tetrahedron method for Brillouin-zone integrations. , 1994, Physical review. B, Condensed matter.

[6]  H. Monkhorst,et al.  SPECIAL POINTS FOR BRILLOUIN-ZONE INTEGRATIONS , 1976 .

[7]  Haas,et al.  Electronic structure of the lead monoxides: Band-structure calculations and photoelectron spectra. , 1995, Physical review. B, Condensed matter.

[8]  J. Leciejewicz.  On the crystal structure of tetragonal (red) PbO , 1961 .

[9]  S. Hull,et al.  The Crystal Structures of Thallium(I) Fluoride , 2000 .

[10]  Nevil Vincent Sidgwick,et al.  Bakerian Lecture: Stereochemical types and valency groups , 1940, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[11]  D. Vanderbilt,et al.  Soft self-consistent pseudopotentials in a generalized eigenvalue formalism. , 1990, Physical review. B, Condensed matter.

[12]  Zeng,et al.  Anisotropic broadening of the linewidth in the EPR spectra of Cr3+ ions in various doped yttrium aluminum garnet single crystals. , 1989, Physical review. B, Condensed matter.

[13]  P. Loubeyre,et al.  The membrane diamond anvil cell: A new device for generating continuous pressure and temperature variations , 1988 .

[14]  M. Kunz,et al.  An improved X-ray detector for use at synchrotrons , 1998 .

[15]  N. N. Greenwood,et al.  Chemistry of the elements , 1984 .

[16]  Adams,et al.  Second-order phase transition in PbO and SnO at high pressure: Implications for the litharge-massicot phase transformation. , 1992, Physical review. B, Condensed matter.

[17]  Peter M. Bell,et al.  Calibration of the ruby pressure gauge to 800 kbar under quasi‐hydrostatic conditions , 1986 .

[18]  A. Zunger,et al.  Self-interaction correction to density-functional approximations for many-electron systems , 1981 .

[19]  D. Louër,et al.  Indexing of powder diffraction patterns for low-symmetry lattices by the successive dichotomy method , 1991 .

[20]  Georg Kresse,et al.  AB INITIO CALCULATION OF THE ORIGIN OF THE DISTORTION OF ALPHA -PBO , 1999 .

[21]  R. J. Hill.  Refinement of the structure of orthorhombic PbO (massicot) by Rietveld analysis of neutron powder diffraction data , 1985 .

[22]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[23]  T. Groy,et al.  Splitting of high-temperature X-ray diffraction profiles during the PbO tetragonal ⇄ orthorhombic phase transformation , 1989 .