Analytical gradients for LEDO-DFT

Abstract

We present an implementation of the limited expansion of diatomic overlap density functional theory (LEDO-DFT) including the determination of analytical gradients in the TURBOMOLE program package. LEDO-DFT is a recently developed formalism in the framework of Kohn–Sham density functional theory exhibiting a formal scaling behaviour with N being the number of basis functions. Numerical results obtained with the Ahlrichs split valence plus polarization basis set (SVP) and a preliminary auxiliary basis set for a test set of small molecules demonstrate the accuracy of electronic energies, structural parameters and harmonic frequencies. Compared to the corresponding full Kohn–Sham model, the total energies are typically affected by 10−3au and the computed structure parameters by 0.1pm in bond distances and 0.1° in bond angles. Harmonic frequencies coincide within a few wavenumbers. Larger deviations can be attributed to deficiencies in the preliminary auxiliary basis set. Results for linear alkanes suggest that LEDO-DFT should be very suitable for electronic structure calculations of large molecular systems.