The significance of negativity of the target density in Frozen-Density Embedding Theory based simulations

15 April 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

The accuracy of any observable derived from multi-scale simulations based on Frozen- Density Embedding Theory (FDET) is affected by two inseparable factors: i) the nad approximation for the E xcT [ρ A , ρ B ] term in the FDET expression for the total energy and ii) the choice of the density ρ B (r) for which the FDET eigenvalue equation for the embedded wave-function is solved. If ρ B is locally larger than the exact density of the total system ρ AB , the difference ρ AB (r) − ρ B (r) (target density) cannot be obtained from FDET. For an arbitrary choice for ρ B , FDET provides only the upper bound of the exact energy. The relative significance of these two factors is investigated for four representative weakly bound intermolecular clusters and various choices for ρ B . It is shown that the violation of the non-negativity condition is the principal source of error in the FDET energy if ρ B is the density of the isolated environment, i.e., is generated without taking into account the interactions with the embedded species. Reduction of both the magnitude of the violation of the non-negativity condition and the error in the FDET energy can be pragmatically achieved by means of the explicit treatment of the electronic polarisation of the environment.

Keywords

FDET
Frozen-Density Embedding Theory
multiscale methods
embedding
DFT
subsystem DFT
polarisation

Supplementary materials

Title
Description
Actions
Title
Supplementary Material
Description
A simple proof of the bounds for a parameter used in the manuscript. Tables for numerical values present in Figures
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.