SUMMARYThis paper proposes a formulation of dynamic contact problems which enables exact algorithmic conservation of linear momentum, angular momentum, and energy in ÿnite element simulations. It is seen that a Lagrange multiplier enforcement of an appropriate contact rate constraint produces these conservation properties. A related method is presented in which a penalty regularization of the aforementioned rate constraint is utilized. This penalty method sacriÿces the energy conservation property, but is dissipative under all conditions of changing contact so that the global algorithm remains stable. Notably, it is also shown that augmented Lagrangian iteration utilizing this penalty kernel reproduces the energy conserving (i.e. Lagrange multiplier) solution to any desired degree of accuracy. The result is a robust, stable method even in the context of large deformations, as is shown by some representative numerical examples. In particular, the ability of the formulation to produce accurate results where more traditional integration schemes fail is emphasized by the numerical simulations.

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There has been significant increase in use of

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Developing novel materials for the conversion of solar to chemical energy is becoming an increasingly important endeavour. Perovskite compounds based on bandgap tunable oxynitrides represent an exciting class of novel photoactive materials. To date, literature mostly focuses on the characterization of oxynitride powder samples which have undeniable technological interest but do not allow the investigation of fundamental properties such as the role of the crystalline quality and/or the surface crystallographic orientation toward photo-catalytic activity. The challenge of growing high quality oxynitride thin films arises from the availability of a suitable substrate, owing to strict material and processing requirements: effective lattice matching,