Dielectric Function of Epitaxially Strained Indium Oxide.

Calculation of optical properties of semiconducting materials is a very slowly converging process with respect to k-point sampling in the the Brillouin zone. Such a calculation of particular importance is the change in optical response for ultra-thin epitaxially strained Indium Oxide, which is used as transparent conducting oxide in optoelectronic devices. The convergence of the dielectric function is assessed through the change in the high-frequency dielectric constant $(\varepsilon_{\infty})$ with respect to k-point sampling.
On the HECToR Phase 2b system, using a standard compilation of VASP 5.2, the maximum k-point density possible within the queue limit of twelve hours is $2\times 2\times 2$ using 96 cores, while using k-point parallelism this can be increased to $6\times6\times 6$ and scale up to 1,536 cores. For the latter k-mesh the convergence required is achieved, a result attainable on HECToR only with the k-point parallelized code.