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Viewing upcoming talks containing the keyword: 19
Speaker: Dr Emma McCabe (University of Kent)
Functional materials : insights from experiment and theory E. E. McCabe a*, V. Cascos a, E. Bousquet b a School of Physical Sciences, University of Kent, Canterbury, CT2 7NH, U.K. b Université de Liège , Institut de Physique B5a, Allée du 6 Août,17, B -4000 Sart Tilman, Belgium * e.e.mccabe @kent.ac.uk
Technology is developing at such a rate that the drive for new materials, to enable emerging technologies with functionalities hardly imaginable even a decade ago, has never been more exciting. 1 One class of functional materia ls that serves to illustrate this are ferroelectrics, used in piezoelectric applications and memory devices, 2 but recent developments including in photovoltaics .3-4 Traditional “proper” ferroelectrics rely on the electronic properties of particular ions. There’s been a paradigm shift in th e field with the su ggestion that a new mechanism might be capable of driving the paraelectric to ferroelectric phase transition: by this “hybrid improper” mechanism, combinations of non -polar structural distortions ( e.g. rotations of structural units) stabilise polar cation displacements. 5-6 As a result, the search for new polar materials is flourishing , particularly among classes of layered materials. Our recent work on the Dion -Jacobson family of materials has shown that its possible to tune between the two mechanisms for polar behavio ur in these systems. More recently, our combined experimental and theoretical approach has shown that in many of these layered systems, the parent high -symmetry structure can be stabilised by several distortions leading to many poss ible states of similar energies. We’ve found experimentally that this can cause disorder 7 (which might be exploited to tune properties). 8-9 The presence of metastable states e.g. in Aurivillius phases (see below) also gives the possibility to access ferroelectric and antiferroelectric phases. 10-11 This presentation highlights our recent findings from experimental and computational st udies focusing on the orgins and consequences of disorder and metastable phases. 7, 12
1. Ashley; Greenemeier , Scientific American May 2013, 2013. 2. Scott , Science 2007, 315 (5814), 954 -959. 3. Huang , Nature Photonics 2010, 4, 134 -135 . 4. Butler; Frost; Walsh , Energy Eviron. Sci. 2015, 8, 838 -848. 5. Bousquet; D awber; Stucki; Lichtensteige r; Herme t; Gariglio; Triscone; Ghosez , Nature 2008, 452 , 732 -736. 6. Benedek ; Fe nnie , Phys. Rev. Lett. 2011, 106 , 107204. 7. Casco s; Dove; Bousquet; Levin; St ennett ; Hyatt; Tra n; Halasyamani; Mc Cabe , in preparation Chem. Mater. 2019 . 8. Sto ne; Ophus; Birol; Ciston ; Le e; Wang; F ennie; Schlom; Alem; Gopalan , Nature Commun. 2016, 7, 12572. 9. Birol; Benedek; Fen nie , Phys. Rev. Lett. 2011, 107 , 257602. 10. Yoshid a; A kamatsu; Tsuji; Her nandez; Padmanabhan ; Gupta; Gibb s; Mibu; Murai; Rond inelli; Gopalan; Tanaka ; Fujita , J. Am. Chem. Soc. 2018, 140 , 15690 -15700. 11. Yoshid a; Fujita; Akamtsu; Hernande z; Gupta, A; Brown; Padmanabhan; Gibbs ; Juge; T suj i; Murai; Rondinelli; G opalan; Tanaka , Adv. Funct. Mater. 2018, 2018 , 1801856. 12. Djani ; McCabe ; Fetei ra; Zhang ; Hal asyamani; Bousquet; Ghosez , in preparation for Phys. Rev. B 2019 . b a c Illustration of non -polar ground state of an A -site deficient Aurivillius phase M2BnO3n+3, showing corner - linked BO6 octahedra in blue, and Bi and O sites in purple and red, respectively. Download PDF
On: October 23, 2019 From: 15h30 To: 16h30View talk
Speaker: Dr David Mills (Manchester)
Building precise molecular architectures to maximise f-element properties David P. Mills School of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK. E: firstname.lastname@example.org; W: email@example.com; T: @millsgroupchem. The complexity and richness of synthetic f -element chemistry has attracted increasing attention in recent years. This interest is stimulated jointly by scientific curiosity of a relatively unexplored field and the myriad applications that these elements have found in diverse areas such as organic synthesis, materials science and nuclear fuel cycles. 1 Our research focuses on stabilising f -element complexes with unusual coordination geometries and/or oxidation states , which can provide enhanc ed reactivity and unique physical properties. 1 We mainly utilise bulky bis(silyl)amides and cyclopentadienyls as supporting ligands to stabilise these unusual f -element motifs. H ere we will present some recent h ighlights of this work , such as the first nea r-linear f -element complexes ( 1),2 the first measurements of actinide covalency by pulsed EPR spectroscopy on the Th(III) complex (2)3 and the first isolated f -block metallocenium cations ( 3), which provided record magnetic hysteresis temperatures for the dysprosium analogue in 2017 .4 (1) (2) (3)
References: 1. (a) Lanthanide and Actinide Chemistry , S. Cotton , John Wiley & Sons Ltd , 2005 . 2. (a) C. A. P. Goodwin, N. F. Chilton, G. F. Vettese, E. Moreno Pineda, I. F. C rowe, J. W. Ziller, W. J. Evans and D. P. Mills, Inorg . Chem ., 2016, 55 , 10057; (b) N. F. Chilton , C. A. P. Goodwin, D. P. Mills and R. E. P. Winpenny, Chem. Commun ., 2015, 51 , 101. 3. A. Formanuik, F. Ortu, R. Beekmeyer, A. Kerridge, F. Tuna, E. J. L. McInnes and D. P. Mills, Nature Chem ., 2017, 9, 578. 4. (a) C. A. P. Goodwin, F. Ortu, D. Reta, N. F. Chilton and D. P. Mills, Nature , 2017, 548 , 439; (b) C. A. P. Goodwin, D. Reta, F. Ortu, N. F. Chilton and D. P. Mills, J. Am. Chem. Soc ., 2017, 139 , 18714 ; (c) C. A. P. Goodwin, D. Reta, F. Ortu, J. Liu, N. F. Chilton and D. P. Mills, Chem. Commun ., 2018, 54 , 9182 ; (d) J. Liu, D. Reta, J. Cleghorn, Y. X. Yeoh, F. Ortu, C. A. P. Goodwin, N. F. Chilton, D. P. Mills, Chem . Eur . J., 2 019, DOI:10.1002/chem.201901167 . Download PDF
On: October 30, 2019 From: 15h30 To: 16h30View talk
Cond Mat Seminars
Speaker: Fabrizio Cossu (Asia Pacific Centre for Theoretical Physics)
Interest in transition metal dichalcogenides (materials consisting of van der Waals bonded layers) has been revived due to relatively recent access to synthesis of few layers, where their characteristic structure may result in massive symmetry breaking (e.g., inversion and/or centre), which lead to exotic properties in the electronic structure. Collective phases such as superconductivity and charge density waves, which may be conventional in the bulk, could in principle become unconventional in single layers. Therefore, understanding the mechanisms of emergence of these electronic phases and how they change upon external fields or doping is of great interest. Since the symmetry of the charge density waves induces the symmetry of the superconducting gap [1,2], it is interesting to investigate instances of symmetry change. In NbSe2, charge density waves are incommensurate and follow a triangular modulation 3x3, in the bulk and in single layers . However, zones where the modulation has a stripe character [4,5] have been observed in single layers. By means of ab-initio calculations, we investigate the possible scenarios beneath the occurrence of the stripe phase. In addition, adsorption by transition metals induces a hierarchy change and a reduction of the symmetry in charge density waves ; it may be argued that, due to the nature of the adsorbate, spin-orbit effect may dominate the nature of the collective excitations. Finally, we hint at an incipient charge-spin density wave transition induced by the adsorbate . Nat. Phys. 3, 720 (2007). Phys. Rev. B 85, 224532 (2012). Nat. Phys. 12, 92 (2016). Proc. Natl. Acad. Sci. 110, 1623 (2013). Proc. Natl. Acad. Sci. 115, 6986 (2018). Phys. Rev. B 98, 195419 (2018).
On: October 30, 2019 From: 12h00 To: 13h00View talk
Speaker: Prof Anders Backlund (Uppsala)
Applications of chemography in natural products research The concept of chemography, navigating chemical space, have over the last decade been applied to a number of studies on natural products. It has been demonstrated that the concept of proximity in the ChemGPS -NP eight -dimensional chemical property space can be interpreted as a molecular similarity (Rosén et al., 2009), and hence a proxy for the expected biological activity of a particular compound (Buonfiglio et al., 2015).
Combined with methods to define volumes from asymmetric ‘clouds’ of compound representations, and estimating if a specific compound representation is included in that volume, this provide us with e.g. a way of predicting biological activity for a compound – or indicating that an observed activity might be a result of a novel mode of action (Yang et al., 2017, and Xu et al., 2018). The basis for an efficient exploration of these possibilities, will be the definition of high -quality reference sets for differe nt biological activities, effectively acting as placeholders.
Examples of these applications are demonstrated and discussed.
1. Buonfiglio R, Engkvist O, Várkonyi P, Henz A, Vikeved E, Backlund A, Kogej T. J Chem Inf Mod. 2015; 55: 2375 -2390 . 2. Rosén J, Gottfries J, Muresan S, Backlund A, Oprea T. J Med Chem 2009; 52: 1953 -1962. 3. Xu J -H, Lai K -H, Su Y -D, Chang Y -C, Peng B -R, Backlund A, Wen Z -H, Sung P -J. Marine Drugs 2018; 16: 75 -83. 4. Yang L, Chai C -Z, Yan Y, Duan Y -D, Henz A, Zhang B -L, Backlund A, Yu B -Y. Molecules 2017; 22: 1392 -1408. Download PDF
On: October 31, 2019 From: 14h00 To: 15h00View talk
Physics and Astronomy Colloquia
Speaker: Dr Stijn Wuyts (University of Bath)
Studies of the structural evolution of galaxies since the peak epoch of cosmic star formation 10 billion years ago have matured in recent years by combining the power of deep imaging lookback surveys and highly multiplexed integral-field spectroscopy. With observations from the rest-frame ultraviolet to infrared we not only have a census of the stars within galaxies, but also probe their dust, ionised and molecular gas content. Using diagnostics of gravitational and non-gravitational motions I will discuss the disk nature and mass budget of star-forming galaxies at cosmic noon, their turbulent interstellar medium, and the feedback processes responsible for large-scale galactic outflows. I will contrast early star-forming galaxies to their quiescent counterparts at the same epoch, and will draw connections to their likely descendants at the present day.
On: November 1, 2019 From: 10h00 To: 11h00View talk
Speaker: Dr Anna Peacock (Birmingham)
Advancing metalloprotein design for new functions and applications Anna F. A. Peacock School of Chemistry, University of Birmingham, Edgbaston, B15 2TT, UK. firstname.lastname@example.org De novo designed miniatur e protein scaffolds, such as the coiled coil, offer exciting opportunities for metal ion coordination.  Not surprisingly due to the protein like nature of the scaffold, the large majority of de novo metallocoiled coil examples have focused their efforts on mimicking the active sites of native metalloenzymes. Our approach is to instead to use these artificial proteins as novel ligands for the coordination of xeno metals, with no known biological role, with the view to developing functional systems for val uable applications beyond the scope of nature. We recently reported the design of the first gadolinium coiled coil, which displayed promise as a potential MRI contrast agent. [2,3] We have since interrogated the coordination of various lanthanide ions to o ur coiled coils and have for the first time shown that we can selectively discriminate between Ln(III) ions based on size. As a result we have now designed coiled coils capable of binding two different Ln(III) ions selectively to two different sites (see F igure), and at a defined distance from one another. The opportunities this affords and the potential applications of this new class of lanthanide coiled coils, will be discussed. Generous financial support from The University of Birmingham, the School of Chemistry and EU COST action CM1105 is acknowledged.
References  A. F. A. Peacock, Cur. Opin. Chem. Biol. 17 (2013) 934 -939.  M. R. Berwick et al. , J. Am. Chem. Soc. 136 (2014) 1166 -1169.  M. R. Berwick et al. , Chem. Sci. 7 (2016) 2207 -2216. Download PDF
On: November 6, 2019 From: 14h00 To: 15h00View talk