Accuracy of Density Functional Theory in Prediction of Carbon Dioxide Adsorbent Materials

TL;DR

This study evaluates the accuracy of various density functional theory methods in predicting CO2 interactions with alkali-earth-metal decorated carbon structures, highlighting discrepancies with high-level quantum chemistry calculations and conditions for improved agreement.

Contribution

It provides a comparative analysis of DFT and MP2 methods for modeling CO2 adsorption on AEM-decorated carbons, identifying when DFT can reliably approximate MP2 results.

Findings

DFT results significantly differ from MP2 in gas-adsorption energies.

Hybrid DFT functionals align closely with MP2 when AEM concentration mimics graphene.

Electron correlation errors impact charge transfer and electrostatic interactions.

Abstract

We have performed a thorough computational study to assess the accuracy of density functional theory (DFT) methods in describing the interactions of CO2 with model alkali-earth-metal (AEM, Ca and Li) decorated carbon structures, namely anthracene (C14H10) molecules. We find that gas-adsorption energy and equilibrium structure results obtained with both standard (i.e. LDA and GGA) and hybrid (i.e. PBE0 and B3LYP) exchange-correlation functionals of DFT differ significantly from results obtained with second-order Moller-Plesset perturbation theory (MP2), an accurate computational quantum chemistry method. The major disagreements found can be mostly rationalized in terms of electron correlation errors that lead to inaccurate charge transfers and electrostatic Coulomb interactions between the molecules. Interestingly, we show that when the concentration of AEM atoms in anthracene is tuned to resemble as closely as possible to the electronic structure of AEM-decorated graphene, hybrid exchange-correlation DFT and MP2 methods provide quantitatively similar results. We discuss the implications of our work in modeling and characterization of currently sought carbon capture and sequestration materials.