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We report results of first-principles calculations on the thermodynamic stability of different Sr adatom structures that have been proposed to explain some of the observed reconstructions of the (001) surface of strontium titanate (Kubo and Nozoye 2003 Surf. Sci. 542 177). From surface free energy calculations, a phase diagram is constructed indicating the range of conditions over which each structure is most stable. These results are compared with Kubo and Nozoye's experimental observations. It is concluded that low Sr adatom coverage structures can only be explained if the surface is far from equilibrium. Intermediate coverage structures are stable only if the surface is in or very nearly in equilibrium with the strontium oxide.

We describe two measures of the local atomic density in a monatomic crystal. A new measure has the form of a function of the sum of inverse powers of the neighbour distance, and it is accurate to 2% for six simple crystalline reference structures ranging from diamond to face-centred cubic. For any periodic structure, reproduces the global average density exactly for any uniform dilation or compression in the limit of an infinite cut-off, and to high accuracy with a smooth cut-off. We compare it with a Gaussian measure of local density for large constant-volume strains of the six reference structures. The changes in are an order of magnitude less than the shear strains for bond-length changes of < 10%. However, is even less sensitive to constant-volume strains. is also transferable between structures, provided that a constant self-term (an on-site term) is included in the density. The measure of local density is primarily intended for atomistic simulations of inhomogeneous systems in which the atom-atom interactions or other terms describing the energy depend on the local volume.

The theory of metal - ceramic interfaces is a collection of approaches which are complementary. They range from thermodynamic modelling based on empirical correlations, through the image model of adhesion, semi-empirical tight-binding calculations, to first-principles calculations based on applying the density functional theory or Hartree - Fock theory. This article reviews the present state of theoretical calculations, with particular reference to electronic structure and adhesion. A section on the thermodynamic background clarifies the concept of work of adhesion which is the goal of many calculations. Cluster models and periodic slabs have been considered, both self-consistent and non-self-consistent. The most sophisticated and complete calculations have been made for metals on MgO and alumina. There a consistent picture of the nature of the bonding has emerged, although there are still significant unexplained discrepancies in numerical values.

We investigate the transfer of energy from a harmonically oscillating atom in a metal to the electronic subsystem, using a direct simulation method based on time-dependent tight-binding (TDTB). We present our results in terms of a viscous damping coefficient β to enable direct comparison with previous MD and Langevin dynamics simulations, over an ionic energy range relevant for radiation damage. Analysis of our results using time-dependent perturbation theory shows that the rate of energy transfer to the electrons is independent of the frequency of the driven atom at high electronic temperatures, but at low temperature may vary by an order of magnitude. Our simulations show β also to be dependent on the electronic temperature, the position of the atom within the unit cell and even the direction of oscillation. We conclude that a TDTB simulation can give the electronic damping for an infinite metal over a limited simulation time window dependent on system size, and show how to monitor errors in dynamic simulations due to finite-size effects.