Office 2604
School of Physics and Astronomy
James Clerk Maxwell Building
Peter Guthrie Tait Road
The University of Edinburgh
Edinburgh, EH9 3FD
Phone +44 131 650 5824

About Me

I hold the Chair of Computational Physics in the School of Physics and Astronomy at the University of Edinburgh. My research is in the field of computational materials science: using first-principles, parameter-free computing methods to predict and understand properties of materials – such as their stability, elastic, electronic, and optical attributes.

As member of the Centre for Science at Extreme Conditions, a part of my research focuses on the occurrence of new, interesting phases of various materials under conditions of extreme compression and high temperatures.

Join the Group

Students interested to join the group for a PhD are always welcome. Research projects can be found on the Schoolโ€™s web pages, together with information on the application process.
Potential undergraduate research projects are listed on the Schoolโ€™s wiki page (requires login).


01/2024: Superconductivity in covalent sodalite-like networks
The high-Tc superconductivity in polyhydrides emerges around clathrate-type motifs of the hydrogenic sublattice. Because bonding between atomic hydrogen is weak these structures can not be recovered to ambient pressures. Covalently bound clathrates should have much higher mechanical stability. In this work, just out in J. Mat. Chem. C, we explore Ga- and Ge-doped sodalite carbon networks, and predict superconductivity around nitrogen’s boiling point at ambient pressure.

01/2024: Thermal energy storage in phase change materials
Phase change materials (PCM’s) exhibit temperature-induced solid state phase transitions that can be exploited for thermal energy storage. Most commonly they transform from a crystalline to a plastic phase, with rotating entities on specific lattice sites at high temperature. Here, we investigate the PCM’s KBF4 and NaBF4. Our molecular dynamics simulations confirm the transition to a plastic phase in both compounds, supporting experimental diffraction experiments. The work, led by the Konar group, is now published in Chem. Mater.

01/2024: New H-C-N compounds under pressure
The elements hydrogen, carbon, and nitrogen are prevalent throughout the solar system. Under extreme conditions as found within planetary bodies, what types of compounds would they form? Here, high-pressure and -temperature synthesis results in two new phases of C(NH)2. Our calculations corroborate the experimental structural assignment. This collaborative effort is now published in Angewandte Chemie. Note that one of the new phases emerged from our previous exploration of the H-C-N-O chemical space.

01/2024: Alkali polyhydrides, revisited
The first computational investigations of metal polyhydrides were detailed studies of mixtures of alkali metals with hydrogen. Experimental evidence has always been sparse due to challenging synthesis conditions. Now, led by the Peรฑa-Alvarez group, we provide evidence for the formation of sodium trihydride, NaH3, from diffraction and spectroscopy data combined with first principles simulations, as just reported in Front. Chem. The non-formation of any higher hydride is important here, and provides important benchmarks for future computational and experimental investigations.

12/2023: Water carriers in the deep Earth
The deep water cycle connects Earth’s surface water to storage reservoirs deep within Earth’s mantle, with exchange on geological timescales via plate tectonics and mantle convection processes. But what are these storage reservoirs? We previously suggested new mineral structures relevant in the upper mantle. Now, we explored new compounds stable at lower mantle conditions. A new iron silicate hydrate phase, FeSiO3.H2O, emerged as a promising materials candidate under those conditions. Based on large-scale structure searching of a large quasi-ternary chemical composition space, this work led by the Ma group at Jilin University has now appeared in Phys. Rev. B.

11/2023: Anderson localization of phonons in partially deuterated ice
When is the whole not the sum of its parts? In partially deuterated water or ice, rapid proton-deuteron exchange leads to an equilibrium distribution of H2O/HOD/D2O molecules. The vibrational properties of the isotopic mixture can not be explained via the isotopically pure substances. Instead, local H/D disorder leads to a multitude of vibrational eigenmodes and a broad distribution of frequencies, a phenomenon hitherto only seen in very dense H2-D2 mixtures. Our calculations, in collaboration with the Glenzer group from SLAC Stanford, explained the character of phonon localization in this simple system, and have been published in Phys. Rev. Research.

11/2023: Charge density wave mechanism in sulfur
Charge density waves (CDW’s) are of interest in 2D materials but also occur in elements – mostly under pressure. How does a CDW form and disappear as pressure is changed? Here, we investigate this question for elemental sulfur, in collaboration with the Friedemann group in Bristol, who tracked the CDW amplitude mode with Raman spectroscopy. Our calculations then helped explain how the disappearance of the CDW at the upper pressure limit is due to a weakly first-order transition, due to coupling of the CDW amplitude to a lattice distortion. This nice collaborative work has just been published in Phys. Rev. Research.

10/2023: When nobles get together
Pressure can induce the formation of stoichiometric compounds of noble gases, but predictions have outweighed experimental evidence so far. Here, in collaboration with the Gregoryanz group, we confirm the formation of XeAr2 under pressure, in the hexagonal Laves phase structure, adding a valuable data point to the field. This work has now been published in J. Chem. Phys.

06/2023: Ternary hydride superconductors
Metal polyhydrides, especially if they include rare earth metals, have been shown to hold promise for high-temperature superconductivity. Can hydrides of main group elements compete? Here, just published in Phys. Rev. B, we show that ternary hydrides formed from a sodium-phosphorous backbone can indeed be high-temperature superconductors.

03/2023: Review on crystal structure prediction
We contributed a review article on “First-principles crystal structure prediction” to the third edition of Comprehensive Inorganic Chemistry, an excellent reference handbook not just for inorganic chemists.

09/2022: Leo joins the group
Leopoldine (Leo) Parczanny joins the group as new doctoral student. Leo will work on high-temperature states of planetary ices – welcome to the group, Leo!

06/2022: Dimerization in hot dense lithium
Lithium, a prototypical simple metal at ambient conditions, was famously predicted to form dimers at high pressures. This sparked a paradigm shift, with the realisation that high-pressure physics does not necessarily end up with simple close packing of atoms but instead quite complex structures. The dimerised lithium structures never materialised – until now, as we found hints of their formation in a high-temperature phase around lithium’s melting point minimum. The work, in close collaboration with Prof Sun from Nanjing University, is now published in Phys. Rev. B.

05/2022: Quantum solids vs sphere packings: methane-hydrogen mixtures
When methane and hydrogen mix under pressure, they form a series of compounds. We have now revised the 25-year old phase diagram of those compounds, based on painstaking experimental diffraction and spectroscopy work headlined by Dr Howie, accompanied by our electronic structure calculations. In the process we established the material that stores the most amount of molecular hydrogen by weight, and another that features the highest molecular vibrational frequency in any compound. Results now published in Phys. Rev. Lett., and featured in APS Physics.

04/2022: Dr Conway
Lewis has successfully defended his thesis entitled “Elements of Life under Pressure: Chemistry and Crystal Structures of H-C-N-O Compounds in Planetary Interiors”. Many congratulations Lewis, and best of luck in your next role, at the University of Cambridge.

03/2022: Elastic response of subduction slabs
Oceanic tectonic plates are ‘wet’, they carry water into the deep Earth in subduction slabs that are pushed below continental plates. The water is stored inside minerals, initially (at low depths) in clay-based materials. Talc is a prototypical water carrier and its elastic response under pressure is crucial for explaining seismological observations in subduction slabs. Our ab initio calculations of talc’s elastic constants, just published in Geosci. Front., show it has anomalous features that could explain seismological features of subduction systems.

01/2022: New sulfur oxides help explain volcanic paradox
Volcanic eruptions emit more sulfur than should be stored in the magma. The ‘sulfur excess’ paradox could be explained by hitherto unknown sulfur reservoirs in Earth’s deep mantle. Here, in work led by Dr Wang from Jilin University and just published in Sci. Bull., we report a new sulfur oxide, S3O4, to become stable at lower mantle pressure conditions, and which could therefore act as the missing sulfur reservoir.

01/2022: Understanding ammonia-water mixtures
The ammonia-water phase diagram is very rich, with at least three different stoichiometric compositions, each with numerous phases found at different pressure-temperature conditions. These compounds have the potential to significantly influence the interior structure of icy moons and planets, as well as provide hints at potential gas hydrates that can have technological implications, yet many of them are unsolved. Extremely difficult neutron diffraction experiments led by Dr Loveday and his group, supported by our calculations, now identified a promising structural candidate for ammonia monohydrate IV, as reported in Crystals.