PNOF5 calculations based on the “thermodynamic fragment energy method”: $$\mathrm{C}_{n}\mathrm{H}_{2n+2}(n=1,10)$$ and $$\mathrm{(FH)}_{n}(n=1, 8)$$ as test cases

Abstract

The performance of the “thermodynamic fragment energy method” (FEM) in the context of natural orbital functional theory (NOFT) in its PNOF5 implementation is assessed. Two test cases are considered: the linear chains \(\mathrm{C}_{n}\mathrm{H}_{2n+2}(n=1,10)\) and the hydrogen-bonded \(\mathrm{(FH)}_{n}(n=1, 8)\) clusters. Calculations show a fast convergence of the PNOF5-FEM method, which allows the treatment of extended system at a fractional cost of the whole calculation. We show that this type of methodologies could expand the range of systems achievable by NOFT due to the significant reduction in the computational cost.