Prof. John S.O. Evans, (Director of Research)
(email at email@example.com)
My principal research interests lie in the field of solid state chemistry and involve the synthesis, characterisation and evaluation of new materials of potential industrial and academic interest. The technological impact of solid state chemistry over the last few decades has been immense, and has affected almost every aspect of our daily lives. Examples include the zeolite catalysts used in the petroleum industry, the magnetic materials used for data storage in modern computers, and the high temperature superconductors which have the potential to revolutionise a large number of technologies.
Recent areas of research (some of which are described in more detail below) include negative thermal expansion materials - materials that actually contract in volume when heated, new oxychalcogenide layered intergrowths, new chalcogenide materials, intercalation chemistry, the synthesis, properties and applications of magnetic nanoparticles and new ternary bismuth-containing oxides. These projects all contain elements of synthesis and characterisation and research students could expect to receive training in X-ray and neutron diffraction techniques, conductivity measurements, magnetic measurements and solid state NMR.
One of the major techniques for studying materials is powder diffraction. The group has state of the art powder diffractometers capable of measuring samples from 10 to 1500 K. These are used to follow the progress of reactions as a function of temperature and time, giving valuable insight into chemical processes and mechanistic pathways in the solid state. We are also interested in structure solution/refinement from powder data and several of the most complex structure solutions performed to date have come from our group. We are active in the development of methods for structural analysis, such as "surface fitting" of powder diffraction data and "distortion mode" analysis (with collaborators at Brigham Young) for understanding phase transitions and magnetic structures. We work closely with Alan Coelho on developing the topas academic software suite for powder diffraction. We also collaborate with colleagues at central facilities on techniques such as total scattering (the PDF method) for understanding correlated motion in materials and to probe the short range structure of amorphous materials. We have excellent in-house synthesis and characterization facilities including a new Quantum Design SQUID magnetometer and Physical Properties Measurement System. We work with others in Durham and elsewhere on single crystal diffraction, solid state NMR, neutron diffraction and conductivity measurements. The combination of facilities and expertise available make Durham a wonderful place to perform solid state research.
Negative Thermal Expansion and Framework Materials
A major area of interest is in the field of negative thermal expansion (NTE) - that is materials which contract when heated. Cubic zirconium tungstate, for example, contracts continuously over a previously unprecedented temperature range of 2 to 1050K. Such materials have a range of potential applications. In addition to its negative thermal expansion, ZrW2O8 exhibits oxide ion mobility at 450 K and unusual behaviour under applied pressure. Related materials such as ZrWMoO8 and ZrMo2O8 show oxygen migration at temperatures as low as 200 K.
We have been active in understanding both the synthetic routes to these materials and why they show such interesting behaviour. This property is not restricted to oxide materials and we've recently described "colossal" contraction in the framework cyanide Ag3[Co(CN)6] with colleagues from Cambridge and ISIS.
New Oxychalcogenides and Chalcogenides
Whilst there has been considerable research into both oxide and chalcogenide phases, relative little is known about materials containing simultaneously both oxide and chalcogenide anions. Interest in this area has grown enormously in recent years due to the discovery of superconductivity at remarkably high temperatures in systems such as LaOFeAs and FeSe. We have prepared a number of new, oxychalcogenides such as Bi2YO4Cu2Se2, with interesting magnetic and conduction properties.
Left: key structures involved in the synthetic pathway to ZrMo2O8 - a material that actually contracts in volume on heating. Right: the structure of the oxychalcogenide Bi2YO4Cu2Se2
- "Direct Synthesis of Cubic ZrMo2O8 Followed by Ultrafast In Situ Powder Diffraction", J.E. Readman, S.E. Lister, L. Peters, J. Wright, and J.S.O. Evans, Journal of the American Chemical Society, 131, 2009, 17560-17562.
- "Colossal positive and negative thermal expansion in the framework material Ag3Co(CN)6", A.L. Goodwin, M. Calleja, M.J. Conterio, M.T. Dove, J.S.O. Evans, D.A. Keen, L. Peters, and M.G. Tucker, Science, 319, 2008, 794-797.
- "Structural and Mechanistic Studies of the Dehydration of MoO2PO3OH.H2O and the In situ Identification of Two New Molybdenum Phosphates", S.E. Lister, V.J. Rixom, and J.S.O. Evans, Chemistry of Materials, 22, 2010, 5279-5289.
- "Local structure in ZrW2O8 from neutron total scattering", M.G. Tucker, D.A. Keen, J.S.O. Evans, and M.T. Dove, Journal of Physics-Condensed Matter, 19, 2007.
- "Parametric Rietveld refinement", G.W. Stinton and J.S.O. Evans, Journal of Applied Crystallography, 40, 2007, 87-95.
- "Structural description of pressure-induced amorphization in ZrW2O8", D.A. Keen, A.L. Goodwin, M.G. Tucker, M.T. Dove, J.S.O. Evans, W.A. Crichton, and M. Brunelli, Physical Review Letters, 98, 2007, 22501.
- "Preparation, Characterization, and Structural Phase Transitions in a New Family of Semiconducting Transition Metal Oxychalcogenides b-La2O2MSe2 (M = Mn, Fe)", E.E. McCabe, D.G. Free, B.G. Mendis, J.S. Higgins, and J.S.O. Evans, Chemistry of Materials, 22, 2010, 6171-6182.
- "A new iron oxyselenide Ce2O2FeSe2: synthesis and characterisation", E.E. McCabe, D.G. Free, and J.S.O. Evans, Chem. Commun., 47, 2011, 1261-1263.
Chapter in book
- Evans, John S.O. (2010). Advanced Input Files & Parametric Quantitative Analysis Using Topas. In Extending the Reach of Powder Diffraction Modelling by User Defined Macros. Scardi, P. Dinnebier R.E. 651: 1-9.
- Araujo, Luiza R., Gallington, Leighanne C., Wilkinson, Angus P. & Evans, John S.O. (2018). Phase behaviour, thermal expansion and compressibility of SnMo 2 O 8. Journal of Solid State Chemistry 258: 885-893.
- Oogarah, R. K., Stockdale, C. P. J., Stock, C., Evans, J. S. O., Wills, A. S., Taylor, J. W. & McCabe, E. E. (2017). Crystal field excitations and magnons: Their roles in oxyselenides Pr2O2M2OSe2 (M = Mn, Fe). Physical Review B 95(17): 174441.
- Ainsworth, C.M., Lewis, J.W., Wang, C.H., Coelho, A.A., Johnson, H.E., Brand, H.E.A. & Evans, J.S.O. (2016). 3D Transition Metal Ordering and Rietveld Stacking Fault Quantification in the New Oxychalcogenides La2O2Cu2–4xCd2xSe2. Chemistry of Materials 28(9): 3184-3195.
- Coelho, A.A., Evans, J.S.O. & Lewis, J.W. (2016). Averaging the intensity of many-layered structures for accurate stacking-fault analysis using Rietveld refinement. Journal of Applied Crystallography 49(5): 1740-1749.
- Shephard, J.J., Callear, S.K., Imberti, S., Evans, J.S.O. & Salzmann, C.G. (2016). Microstructures of negative and positive azeotropes. Physical Chemistry Chemical Physics 18(28): 19227-19235.
- Nunes, Sayonara Eliziario, Wang, Chun-Hai, So, Karwei, Evans, John S.O. & Evans, Ivana Radosavljević (2015). Bismuth zinc vanadate, BiZn2VO6: New crystal structure type and electronic structure. Journal of Solid State Chemistry 222: 12-17.
- Wang, Chun-Hai, Ainsworth, Chris M., Gui, Dong-Yun, McCabe, Emma E., Tucker, Matthew G., Evans, Ivana R. & Evans, John S. O. (2015). Infinitely Adaptive Transition Metal Oxychalcogenides: The Modulated Structures of Ce2O2MnSe2 and (Ce0.78La0.22)2O2MnSe2. Chemistry of Materials 27(8): 3121-3134.
- Ainsworth, Chris M., Wang, Chun-Hai, Johnston, Hannah E., McCabe, Emma E., Tucker, Matthew G., Brand, Helen E. A. & Evans, John S. O. (2015). Infinitely Adaptive Transition-Metal Ordering in Ln2O2MSe2-Type Oxychalcogenides. Inorganic Chemistry 54(15): 7230-7238.
- Shephard, J. J., Soper, A. K., Callear, S. K., Imberti, S., Evans, J. S. O. & Salzmann, C. G. (2015). Polar stacking of molecules in liquid chloroform. Chemical Communications 51(23): 4770-4773.
- Tuxworth, Andrew J., Wang, Chun-Hai & Evans, John S. O. (2015). Synthesis, characterisation and properties of rare earth oxyselenides A4O4Se3 (A = Eu, Gd, Tb, Dy, Ho, Er, Yb and Y). Dalton Transactions 44(7): 3009-3019.
- Ainsworth, Chris M., Wang, Chun-Hai, Tucker, Matthew G. & Evans, John S. O. (2015). Synthesis, Structural Characterization, and Physical Properties of the New Transition Metal Oxyselenide Ce2O2ZnSe2. Inorganic Chemistry 54(4): 1563-1571.
- McCabe, E. E., Stock, C., Bettis, J. L., Jr., Whangbo, M. H. & Evans, J. S. O. (2014). Magnetism of the Fe2+ and Ce3+ sublattices in Ce2O2FeSe2: A combined neutron powder diffraction, inelastic neutron scattering, and density functional study. Physical Review B: condensed matter and materials physics 90(23): 235115.
- McCabe, E. E., Wills, A. S., Chapon, L., Manuel, P. & Evans, J. S. O. (2014). Structural and magnetic characterization of iron oxyselenides Ce2O2Fe2OSe2 and Nd2O2Fe2OSe2. Physical Review B: condensed matter and materials physics 90(16): 165111.
- Tuxworth, A. J. & Evans, J. S. O. (2014). Synthesis, structure and properties of the oxychalcogenide series A4O4TiSe4 (A=Sm, Gd, Tb, Dy, Ho, Er and Y). Journal of Solid State Chemistry 210(1): 188-194.
- McCabe, E. E., Stock, C., Rodriguez, E. E., Wills, A. S., Taylor, J. W. & Evans, J. S. O. (2014). Weak spin interactions in Mott insulating La2O2Fe2OSe2. Physical Review B 89(10): 100402(R).
- Tuxworth, Andrew J., McCabe, Emma E., Free, David G., Clark, Stewart J. & Evans, John S. O. (2013). Structural Characterization and Physical Properties of the New Transition Metal Oxyselenide La2O2ZnSe2. Inorganic Chemistry 52(4): 2078-2085.
- Shephard, Jacob J., Evans, John S. O. & Salzmann, Christoph G. (2013). Structural Relaxation of Low-Density Amorphous Ice upon Thermal Annealing. Journal of Physical Chemistry Letters 4(21): 3672-3676.
- Wood, T.J., Hurst, G.A., Schofield, W.C.E., Thompson, R.L., Oswald, G., Evans, J.S.O., Sharples, G.J., Pearson, C., Petty, M.C. & Badyal, J.P.S. (2012). Electroless deposition of multi-functional zinc oxide surfaces displaying photoconductive, superhydrophobic, photowetting, and antibacterial properties. Journal of Materials Chemistry 22(9): 3859-3867.
- Kerman, Sean, Campbell, Branton J., Satyavarapu, Kiran K., Stokes, Harold T., Perselli, Francesca & Evans, John S. O. (2012). The superstructure determination of displacive distortions via symmetry-mode analysis. Acta Crystallographica Section A 68(2): 222-234.
- McCabe, Emma E., Free, David G. & Evans, John S. O. (2011). A new iron oxyselenide Ce2O2FeSe2: synthesis and characterisation. Chemical Communications 47(4): 1261-1263.
- Coelho, A. A., Evans, John S. O., Evans, Ivana R., Kern, A. & Parsons, S. (2011). The TOPAS symbolic computation system. Powder Diffraction 26(S1): S22-S25.
- Free, David G. & Evans, John S. O. (2010). Low-temperature nuclear and magnetic structures of La2O2Fe2OSe2 from x-ray and neutron diffraction measurements. Physical Review B 81(21): 214433.
- Lister, Sarah E., Rixom, Victoria J. & Evans, John S. O. (2010). Structural and Mechanistic Studies of the Dehydration of MoO2PO3OH center dot H2O and the In situ Identification of Two New Molybdenum Phosphates. Chemistry of Materials 22(18): 5279-5289.
- Keen, David A., Dove, Martin T., Evans, John S. O., Goodwin, Andrew L., Peters, Lars & Tucker, Matthew G. (2010). The hydrogen-bonding transition and isotope-dependent negative thermal expansion in H3Co(CN)(6). Journal of Physics-Condensed Matter 22(40).
- Lister, Sarah E., Evans, Ivana Radosavljevic & Evans, John S. O. (2009). Complex Superstructures of Mo2P4O15. Inorganic Chemistry 48(19): 9271-9281.
- Scarlett, Nicola V. Y., Madsen, Ian C., Evans, John S. O., Coelho, Alan A., McGregor, Katherine, Rowles, Matthew, Lanyon, Marshall R. & Urban, Andrew J. (2009). Energy-dispersive diffraction studies of inert anodes. Journal of Applied Crystallography 42(3): 502-512.
- Goodwin, Andrew L., Keen, David A., Tucker, Matthew G., Dove, Martin T., Peters, Lars & Evans, John S. O. (2008). Argentophilicity-Dependent Colossal Thermal Expansion in Extended Prussian Blue Analogues. Journal of the American Chemical Society 130(30): 9660-9661.
- Conterio, Michael J., Goodwin, Andrew L., Tucker, Matthew G., Keen, David A., Dove, Martin T., Peters, Lars & Evans, John S. O. (2008). Local structure in Ag3[Co(CN)6]: colossal thermal expansion, rigid unit modes and argentophilic interactions. Journal of Physics: Condensed Matter 20(25): 255225.
- Evans, Ivana Radosavljevic, Howard, Judith A. K., Evans, John S. O., Postlethwaite, Stella R. & Johnson, Mark R. (2008). Polymorphism and hydrogen bonding in cinchomeronic acid: a variable temperature experimental and computational study. CrystEngComm 10(10): 1404-1409.
- Crossland, Clare J., Evans, Ivana Radosavljevic & Evans, John S. O. (2008). Structural chemistry of (PPh4)2M(WS4)2 materials. Dalton Transactions (12): 1597-1601.
- Evans, Ivana Radosavljevic, Howard, Judith A. K. & Evans, John S. O. (2008). Structural ferroelectric phase transition and polymorphism in 2-aminopyridine dihydrogen phosphate. Crystal Growth and Design 8(5): 1635-1639.
- Stinton, G.W., Hampson, M.R. & Evans, J.S.O. (2006). The 136-atom structure of ZrP2O7 and HfP2O7 from powder diffraction data. Inorganic chemistry 45(11): 4352-4358.