arXiv subjects

Nicholas Barrett

Publications and source records attributed to Nicholas Barrett.

3 recordsLinked to original sources

arXiv2018

Polarization dependent chemistry of ferroelectric BaTiO3 (001) domains

Recent works suggest that the surface chemistry, in particular, the presence of oxygen vacancies can affect the polarization in a ferroelectric material. This should, in turn, influence the domain ordering driven by the need to screen the depolarizing field. Here we show using density functional theory that the presence of oxygen vacancies at the surface of BaTiO3 (001) preferentially stabilizes an inward pointing, P-, polarization. Mirror electron microscopy measurements of the domain ordering confirm the theoretical results.

cond-mat.mtrl-sci↗

arXiv2017

Cluster sizes in a classical Lennard-Jones chain

The definitions of breaks and clusters in a one-dimensional chain in equilibrium are discussed. Analytical expressions are obtained for the expected cluster length, $\langle K \rangle$, as a function of temperature and pressure in a one-dimensional Lennard-Jones chain. These expressions are compared with results from molecular dynamics simulations. It is found that $\langle K \rangle$ increases exponentially with $\beta = 1/k_BT$ and with pressure, $P$ in agreement with previous results in the literature. A method is illustrated for using $\langle K \rangle (\beta, P)$ to generate a "phase diagram" for the Lennard-Jones chain. Some implications for the study of heat transport in Lennard-Jones chains are discussed.

cond-mat.stat-mech↗

arXiv2012

Orientation-dependent surface composition of in situ annealed strontium titanate

The surface composition of polycrystalline niobium-doped strontium titanate (SrTiO3 : Nb) is studied using X-ray photoelectron emission microscopy (XPEEM) for many grain orientations in order to characterise the surface chemistry with high spatial resolution. The surface sensitivity is maximised by the use of soft X-ray synchrotron radiation (SR). The grain orientation is determined by electron backscattering diffraction (EBSD). Stereographic plots are used to show the correlation between surface composition and orientation for several grains. Predominant surface terminations are assigned to major orientations.

cond-mat.mtrl-sci↗