On nearsightedness in metallic systems for $\mathcal{O}(N)$ Density Functional Theory calculations: A case study on Aluminum

We investigate the locality of electronic interactions in aluminum as a function of smearing/electronic temperature in the context of $\mathcal{O}(N)$ Density Functional Theory calculations. Specifically, we determine the convergence in energy and atomic forces with truncation region size for smearing of $0.001-0.15$ Ha. We find exponential convergence accompanied by a rate that increases sub-linearly with smearing, with truncation region sizes of $48-64$ Bohr required to achieve chemical accuracy for typical smearing values of $0.001-0.01$ Ha. This translates to $\mathcal{O}(N)$ scaling for systems larger than $\mathcal{O}(1000)$ atoms.