Uni-axial Negative Thermal Expansion in Layered Perovskites

Add to your list(s) Download to your calendar using vCal

• Prof. Arash Mostofi, Imperial College London
• Thursday 25 October 2018, 14:15-15:15
• TCM Seminar Room, Cavendish Laboratory.

If you have a question about this talk, please contact Bartomeu Monserrat.

Using first-principles calculations we explain why pronounced uniaxial negative thermal expansion (NTE) is found in certain layered perovskites, such as Ruddlesden-Popper oxides, but elusive in bulk ABO3 perovskites. We show that there are two key ingredients that determine the extent of NTE : (1) the proximity to a phase transition driven by a soft a phonon mode with negative Gruneisen parameter; and (2) the presence of large off-diagonal components of the elastic compliance tensor that predispose the material to the deformations required for NTE . Whilst both ABO3 and layered perovskites often possess the former, it is the unusually high elastic compliance unique to layered perovskites of certain symmetry that allows NTE to persist over a large temperature range. We show that the anisotropy in compliance in Ruddlesden-Popper oxides increases as a function of the density of interface layers in the material and describe a model for the atomic mechanism that is responsible for this feature. These insights open up the possibility of high-throughput screening of NTE materials using the elastic tensor as a descriptor.

This talk is part of the Theory of Condensed Matter series.

This talk is included in these lists:

• All Cavendish Laboratory Seminars
• All Talks (aka the CURE list)
• Centre for Health Leadership and Enterprise
• Combined TCM Seminars and TCM blackboard seminar listing
• Featured lists
• Lennard-Jones Centre external
• ME Seminar
• Neurons, Fake News, DNA and your iPhone: The Mathematics of Information
• PMRFPS's
• School of Physical Sciences
• TCM Seminar Room, Cavendish Laboratory
• Theory of Condensed Matter
• Thin Film Magnetic Talks
• few29

Note that ex-directory lists are not shown.