### Perspective: Chemical Information Encoded in Electron Density

CONTRERAS-GARCíA Julia1,*(),YANG Weitao2

1. 1 UPMC Univ Paris 06, CNRS, UMR 7616, Laboratoire de Chimie Théorique, case courrier 137, 4 place Jussieu, F-75005, Paris
2 Department of Chemistry, Duke University, Durham, NC 27708, USA
• 收稿日期:2017-11-22 发布日期:2018-03-20
• 通讯作者: CONTRERAS-GARCíA Julia E-mail:contrera@lct.jussieu.fr
• 作者简介:Dr. Contreras-García completed her Ph.D. studies in University of Oviedo with a National grant. She then went to Duke University as a Fulbright student, under the advisory of Prof. Yang. After another year of postdoctoral studies with Andreas Savin, she obtained her position at CNRS attached to Sorbonne University. She is interested in theories of chemical bonding in Euclidian space and the application to high pressure. In 2013 she received the European Award for young researchers in High Pressure
• 基金资助:
the Framework of CALSIMLAB under the Public Grant ANR-11-LABX-0037-01 Overseen by the French National Research Agency (ANR) as Part of the "Investissements d'Avenir" Program(ANR-11-IDEX-0004-02);the National Science Foundation(CHE-1362927);the National Institute of Health, USA(R01-GM061870)

### Perspective: Chemical Information Encoded in Electron Density

Julia CONTRERAS-GARCíA1,*(),Weitao YANG2

1. 1 UPMC Univ Paris 06, CNRS, UMR 7616, Laboratoire de Chimie Théorique, case courrier 137, 4 place Jussieu, F-75005, Paris
2 Department of Chemistry, Duke University, Durham, NC 27708, USA
• Received:2017-11-22 Published:2018-03-20
• Contact: Julia CONTRERAS-GARCíA E-mail:contrera@lct.jussieu.fr
• Supported by:
the Framework of CALSIMLAB under the Public Grant ANR-11-LABX-0037-01 Overseen by the French National Research Agency (ANR) as Part of the "Investissements d'Avenir" Program(ANR-11-IDEX-0004-02);the National Science Foundation(CHE-1362927);the National Institute of Health, USA(R01-GM061870)

In this perspective, we review the chemical information encoded in electron density and other ingredients used in semilocal functionals. This information is usually looked at from the functional point of view: the exchange density or the enhancement factor are discussed in terms of the reduced density gradient. However, what parts of a molecule do these 3D functions represent? We look at these quantities in real space, aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology (QCT). Generalized gradient approximations (GGAs) provide information about the presence of chemical interactions, whereas meta-GGAs can differentiate between the different bonding types. By merging these two techniques, we show new insight into the failures of semilocal functionals owing to three main errors: fractional charges, fractional spins, and non-covalent interactions. We build on simple models. We also analyze the delocalization error in hydrogen chains, showing the ability of QCT to reveal the delocalization error introduced by semilocal functionals. Then, we show how the analysis of localization can help understand the fractional spin error in alkali atoms, and how it can be used to correct it. Finally, we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1, 3-interactions.

Abstract:

In this perspective, we review the chemical information encoded in electron density and other ingredients used in semilocal functionals. This information is usually looked at from the functional point of view: the exchange density or the enhancement factor are discussed in terms of the reduced density gradient. However, what parts of a molecule do these 3D functions represent? We look at these quantities in real space, aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology (QCT). Generalized gradient approximations (GGAs) provide information about the presence of chemical interactions, whereas meta-GGAs can differentiate between the different bonding types. By merging these two techniques, we show new insight into the failures of semilocal functionals owing to three main errors: fractional charges, fractional spins, and non-covalent interactions. We build on simple models. We also analyze the delocalization error in hydrogen chains, showing the ability of QCT to reveal the delocalization error introduced by semilocal functionals. Then, we show how the analysis of localization can help understand the fractional spin error in alkali atoms, and how it can be used to correct it. Finally, we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1, 3-interactions.