In this work we apply first principles calculations to investigate the stability trends of mixed boron, nitrogen and carbon diamondol-like compounds. Several distinct geometric models are tested by varying the stoichiometry and position of boron and nitrogen dopants. We verify the special stability of a complete boron nitride compound – the bonitrol –, and we show that carbon substitutions in the bonitrol structure may also lead to stable systems. The electronic characterization of the resulting compounds indicates a rich phenomenology, with metallic, semimetallic, half-metallic and semiconducting behaviors.
We propose a unimodular version of the Brans–Dicke theory designed with a constrained Lagrangian formulation. The resulting field equations are traceless. The vacuum solutions in the cosmological background reproduce the corresponding solutions of the usual Brans–Dicke theory but with a cosmological constant term. A perturbative analysis of the scalar modes is performed and stable and unstable configurations appear, in contrast with the Brans–Dicke case for which only stable configurations occur. On the other hand, tensorial modes in this theory remain the same as in the traditional Brans–Dicke theory.