ONETEP + TOSCAM: Uniting Dynamical Mean Field Theory and Linear-Scaling Density Functional Theory.

Edward B Linscott,Nicholas D M Hine,Daniel J Cole,Cédric Weber,Michael C Payne

doi:10.1021/acs.jctc.0c00162

Abstract

We introduce the unification of dynamical mean field theory (DMFT) and linear-scaling density functional theory (DFT), as recently implemented in ONETEP, a linear-scaling DFT package, and TOSCAM, a DMFT toolbox. This code can account for strongly correlated electronic behavior while simultaneously including the effects of the environment, making it ideally suited for studying complex and heterogeneous systems that contain transition metals and lanthanides, such as metalloproteins. We systematically introduce the necessary formalism, which must account for the nonorthogonal basis set used by ONETEP. In order to demonstrate the capabilities of this code, we apply it to carbon monoxide ligated iron porphyrin and explore the distinctly quantum-mechanical character of the iron 3d electrons during the process of photodissociation.

Highlights

In the past few decades, density functional theory (DFT) has established itself as a key method in computational materials science.[1−4] Facilitated by exponentially increasing computing power, modern DFT codes are capable of routinely calculating the electronic structures of hundreds of atoms, opening the door to quantum-mechanical modeling of a vast landscape of systems of considerable scientific interest
This paper introduces the implementation of TOSCAM (A TOolbox for Strongly Correlated Approaches to Molecules) on top of ONETEP, a linear-scaling DFT code
To demonstrate the use of the ONETEP + TOSCAM interface, the second half of this paper presents some calculations on an archetypal strongly correlated system: an iron porphyrin ring with imidazole and carbon monoxide as the axial ligands (FePImCO) shown in Figure 6a, a toy model for the full carboxymyoglobin complex (Figure 6b)

Summary

INTRODUCTION

In the past few decades, density functional theory (DFT) has established itself as a key method in computational materials science.[1−4] Facilitated by exponentially increasing computing power, modern DFT codes are capable of routinely calculating the electronic structures of hundreds of atoms, opening the door to quantum-mechanical modeling of a vast landscape of systems of considerable scientific interest. Many of these stem from its approximate treatment of exchange and correlation via an exchange−correlation (XC) functional These shortcomings become especially evident in “strongly correlated” systems, which typically contain transition element or rare-earth atoms whose 3d- or 4f-electron shells are partially filled. DFT often yields magnetic moments inconsistent with experiment,[15] predicting some insulators to be metallic,[16,17] and yielding equilibrium volumes dramatically different from experiment.[18] DFT fails to capture important dynamic properties that are enhanced by strong correlation, such as satellite peaks in photoemission spectra.[19,20] These cases motivate the need for more accurate theories. This paper presents an overview of this methodology, its implementation, and an example of its application

THEORY

IRON PORPHYRIN

CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES