Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes

Abstract

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Bader charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. We conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.

Introducing DDEC6 atomic population analysis: part 1. Charge partitioning theory and methodology

“…(4) The original Hirshfeld (HD) 18 method, which is based on neutral reference atom densities, usually underestimates NAC magnitudes. 20,23 The CM5 charges include an empirical correction to the HD NACs. (5) The Charge Model 5 (CM5) was parameterized to give NACs that approximately reproduce static molecular dipole moments.…”

“…[19][20][21][22] While the Iterative Hirshfeld (IH) method improves the NAC magnitudes, 21 it exhibits the bifurcation problem described in Section 2.4. 20,23 The main limitation of CM5 is that it only partitions the integrated number of electrons for each atom, and thus cannot be used to compute AIM properties such as atomic multipoles, bond orders, etc. 20,23 The CM5 charges include an empirical correction to the HD NACs.…”

Mononuclear Dysprosium(III) Complexes with Triphenylphosphine Oxide Ligands: Controlling the Coordination Environment and Magnetic Anisotropy

“…We used the Loprop charges to understand the direction of magnetic anisotropy which is a static property, which can be computed like a charge, a component of the dipole moment or an exchange-hole dipole moment [38], is localized by transforming the property of two centers [39,40]. The temperature dependence of the magnetic susceptibility is calculated in the temperature range from 0 to 300 K for all complexes and is tabulated in Table S8.…”

Electronic structure theory to decipher the chemical bonding in actinide systems

“…There are many possible methods that could be used to determine reasonable atomic charges. It is critical to model the electrostatic interactions at an acceptable level of accuracy since the resulting charges on interior atoms of a molecular system can be unstable and may have unphysical values [29][30][31]. This approach will not be discussed here.…”