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Mr Edgar Engel
Research Fellow at Trinity College
Fellow of Trinity College
Office: 514 Mott Bld
Phone: +44(0)1223 3 37278
Email: eae32 @ cam.ac.uk
TCM Group, Cavendish Laboratory
19 JJ Thomson Avenue,
Cambridge, CB3 0HE UK.
My interest lies describing quantum condensed matter system using electronic structure methods ranging from simple, inexpensive empirical force fields to more accurate and expensive first-principles density functional theory (DFT).
My current focus is the structures and properties of various water ice phases both in their bulk forms and at surfaces. Properties of interest include primarily the bulk and surface free energies of ice including contributions from (anharmonic) nuclear vibrations as well as the electronic band gaps and their renormalisation due to nuclear vibrations both at zero and nonzero temperature. I also employ (ab initio) random structure searching (AIRSS) techniques to understand the large scale reorganisation of the hydrogen bridge network upon introduction of a defect into the perfect crystal structure. Defect formation energies are strongly correlated with the reactivity and pre-melting properties of ice surfaces.
In Plain English
The macroscopic properties of various materials, like their melting/freezing point, density, etc. are often easily accessible in experiment and are mostly well known. Our atomistic and mechanistic understanding of their structure and properties, on the other hand, is generally far from complete. This is where atomistic modelling comes in.
A prime example of such a material is water ice. Plain water ice is a surprisingly complicated material to understand for multiple reasons. It has a highly complicated phase diagram with currently 16 (meta-)stable crystalline phases. Several additional phases have been proposed and are being investigated. At the same time we are still far from understanding the properties of the ice phases we are most familiar with, hexagonal ice (which occurs in abundance at ambient conditions on earth as snow and ice) and its elusive twin, cubic ice. From a structural perspective cubic ice is very similar to hexagonal ice. It is extremely difficult to synthesise, but might play an important role in ice nucleation processes.
In my work I employ atomistic modelling techniques with the aim to take a few steps towards a more complete understanding of various ice phases.
- Anharmonic nuclear motion and the relative stability of hexagonal and cubic ice Physical Review X 5 021033 (2015)
- Giant electron-phonon interactions in molecular crystals and the importance of non-quadratic coupling Physical Review B 92 140302(R) (2015)
- Vibrational renormalisation of the electronic band gap in hexagonal and cubic ice Journal of Chemical Physics 143 244708 (2015)