BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Complex materials: A journey from disappearing ice phases and ‘p
 ink’ phosphorus to stacking disordered silver iodide - Prof. Christoph G
 . Salzmann (University College London)
DTSTART:20190425T130000Z
DTEND:20190425T140000Z
UID:TALK122917@talks.cam.ac.uk
CONTACT:Lingtao Kong
DESCRIPTION:The research activities of our group focus on the structural c
 haracterisation of complex materials including disordered crystals\, amorp
 hous\, glassy and nanomaterials as well as liquids. Our keen ambition is t
 o establish links between the atomic structure of materials\, and their ch
 emical and physical properties and performances. Building on this\, we als
 o investigate complex phase transitions\, crystallisation phenomena\, chem
 ical reactions in confinements as well as the chemical functionalisation o
 f nanomaterials including carbon nanotubes and graphene. In this talk\, I 
 will present an overview over our most recent work including the following
  topics:\n(1) Doping-induced disappearance of ice II from the phase diagra
 m. Ammonium fluoride acts as a ‘magic ingredient’ that enables us to l
 et ice II disappear from the phase diagram in a highly selective fashion.[
 1] A detailed understanding of the underlying mechanisms and thermodynamic
 s is presented\, and we argue that our new finding has wider implications 
 that enables us to understand some of the anomalies of water’s phase dia
 gram including the anomalous properties of liquid water. The selective dis
 appearance of a particular phase with the aid of a dopant highlights the e
 xciting possibility of potentially discovering new phases of ice but also 
 other materials in the future using specific impurities.\n(2) New 1D allot
 ropes of phosphorus and arsenic. The pnictogen nanomaterials\, including p
 hosphorene and arsenene\, display remarkable electronic and chemical prope
 rties. Yet\, the structural diversity that these main group elements are c
 apable of is still poorly explored. We filled single-wall carbon nanotubes
  with elemental phosphorus and arsenic from the vapour phase.[2\,3] Using 
 electron microscopy\, chains of highly reactive P4 and As4 molecules were 
 found as well as new one-dimensional allotropes: a single-stranded zig-zag
  chain and a double-stranded zig-zag ladder. These linear structures repre
 sent important intermediates between the gas-phase clusters of the pnictog
 ens and the extended 2D sheets of phosphorene and arsenene. Remarkably\, b
 and-gap calculations predict that the insulating P4 and As4 chains become 
 semiconducting\, once converted to the zig-zag ladder\, and form fully met
 allic allotropes in the form of the zig-zag chain.\n(3) Stacking disorder 
 everywhere! Stacking-disordered materials consist of structurally well-def
 ined layers that are stacked on top of one another in a disordered fashion
 . Naturally\, stacking disorder is found for a wide range of layered mater
 ials such as graphite or molybdenum sulphide. Using our MCDIFFaX program\,
  we can model the diffuse diffraction features that arise from stacking di
 sorder and obtain quantitative insights into the extents of different type
 s of stacking as well as memory effects within the stacking sequences. Fol
 lowing extensive work on stacking disorder in ice and diamond\, we have no
 w identified a first system\, silver iodide\, where the stacking disorder 
 can be controlled in a quantitative fashion.[4] This now offers the fascin
 ating prospect of being able to fine-tuning the physical and chemical prop
 erties of a material between the extreme polytypic endmembers.\n \n[1]   J
 .J. Shephard\, B. Slater\, P. Harvey\, M. Hart\, C.L. Bull\, S.T. Bramwell
 \, C.G. Salzmann\, Nat. Phys.\, 14 (2018) 569–572\n[2]   M. Hart\, E.R. 
 White\, J. Chen\, C.M. McGilvery\, C.J. Pickard\, A. Michaelides\, A. Sell
 a\, M.S.P. Shaffer\, C.G. Salzmann\, Angew. Chem. Int. Ed. 56 (2017) 8144-
 8148\n[3]   M. Hart\, J. Chen\, A. Michaelides\, A. Sella\, M.S.P. Shaffer
 \, C.G. Salzmann\, Angew. Chem. Int. Ed. 57 (2018) 11649-11653\n[4]   R.L.
  Smith\, M. Vickers\, M. Rosillo-Lopez\, C.G. Salzmann\, Cryst. Growth Des
 . 19 (2019) 2131-2138
LOCATION:Wolfson Lecture Theatre\,  Department of Chemistry\, Lensfield Ro
 ad
END:VEVENT
END:VCALENDAR