Structural and electronic properties of crystals of thiolate-capped Au nanoparticles doped with donor and acceptor molecules: first-principles calculations

Structural and electronic properties of crystals of etiolate- capped Au nanoparticles doped with donor and acceptor molecules: first-principles calculations We perform first-principles calculations for crystals composed of periodic assemblies of Au$_{38}$ nanoparticles that are capped with methylthiol molecules. We consider fcc structures, consistent with recent experimental results [1]. We also consider that the nanoparticle crystals can be doped with either donor (tetrabutylammonium) or acceptor (hexafluorophosphate) molecules, also consistent with recent experiments [2]. We find that the most stable positions of the dopant molecules are located near the nanoparticle surfaces, and not near interstitial positions. We also find that the electron chemical potential changes linearly with the impurity concentration, up to a critical concentration, consistent with recent experiments [2]. Above that critical concentration, a new regime is observed due to a partial charge transfer between dopants and nanoparticles. These features are reproduced by a simple capacitive model for the crystal. [1] Ab\'ecassis et al. Phys. Rev. Lett. 100, 115504 (2008) [2] Boettcher S. W. et al. Nature Mater. 6, 592–596 (2007).