Large-Scale Quantum-Mechanical Simulations of Nanoscale Devices and New Materials

Recent advances in theoretical methods and high performance computing allow for reliable first-principles investigations of nanoscale devices and complex materials. Using large scale O(N) real-space-based ab initio calculations, we carried out a theoretical study of carbon nanotube-cluster composites as prototype systems for molecular sensing at the nanoscale. Dramatic changes in the electrical conductance of the composite are predicted when gas molecules are adsorbed onto the metal clusters. The observed sensitivity and selectivity might suggest new avenues for the design and production of nanotube-based molecular sensors. The second part of this article focuses on calculating and predicting the properties of piezoelectrics, and on "designing" new materials with enhanced piezoelectric response. We consider polymers in the polyvinylidene fluoride (PVDF) family and show that our calculations not only reproduce well the existing experimental data, but also provide a much improved understanding of their polar properties, which leads to a "design" of novel polymers with a BN backbone. The new polymers are predicted to have up to 100% better piezoelectric response and an enhanced thermal stability with respect to their PVDF analogs. Since methods for their synthesis are readily available, they offer a promising avenue for improving ferro and piezoelectric devices.