The importance of nonlinear fluid response in joint density-functional theory studies of battery systems

Abstract

Delivering the full benefits of first principles calculations to battery materials demands the development of accurate and computationally-efficient electronic structure methods that incorporate the effects of the electrolyte environment and electrode potential.Realistic electrochemical interfaces containing polar surfaces are beyond the regime of validity of existing continuum solvation theories developed for molecules, due to the presence of significantly stronger electric fields. We present an ab initio theory of the nonlinear dielectric and ionic response of solvent environments within the framework of joint densityfunctional theory, with precisely the same optimizable parameters as conventional polarizable continuum models. We demonstrate that the resulting nonlinear theory agrees with the standard linear models for organic molecules and metallic surfaces under typical operating conditions. However, we find that the saturation effects in the rotational response of polar solvent molecules, inherent to our nonlinear theory, are crucial for a qualitatively correct description of the ionic surfaces typical of the solid electrolyte interface. arXiv:1301.6189v1 [cond-mat.mtrl-sci]

The Reaction Mechanism with Free Energy Barriers at Constant Potentials for the Oxygen Evolution Reaction at the IrO2 (110) Surface

“…We computed the grand free energy at the constant electrochemical potential along with the implicit solvation model, in which the charged surfaces can be effectively screened by the ionic response in solution as implemented in JDFTx 8,21,22 . Computational details of JDFTx can be found in SI.…”

Spicing up continuum solvation models with SaLSA: The spherically averaged liquid susceptibility ansatz

“…The RMS errors of SaLSA are only slightly higher than those of the local solvation model from [15] that includes additional fit parameters for the electric response. Figure 3 compares the aqueous solvation energy predictions of SaLSA with those of the linear and nonlinear localresponse models from [14]. All three models perform comparably for the neutral molecule set (Figure 3(a)) used for the parameter fit, but SaLSA is substantially more accurate for inorganic ions (Figure 3(b)).…”

“…Unfortunately, the large number of parameters precludes the extrapolation of these models to systems outside their fit set, such as metallic or ionic surfaces in solution. Recent solvation models that employ an electron-density based parametrization [11,12] require only two or three parameters and extrapolate more reliably, but still encounter difficulties for charged and highly polar systems [13,14].The need for empirical parameters in continuum solvation arises primarily because of the drastic simplification of the nonlocal and nonlinear response of the real liquid with that of a continuum dielectric cavity. Recently, we correlated the dielectric cavity sizes for different solvents with the extent of nonlocality of the solvent response to enable a unified electron-density parametrization for multiple solvents [15], but the electron density threshold n c that determines the cavity size still required a fit to solvation energies of organic molecules.…”

“…The second term of (6) captures the rotational response of solvent molecules with charge distribution ρ mol ( r), decomposed in Fourier space as ρ mol ( G) = lmρ lm mol (G)Y lm (Ĝ). The prefactor C l rot = C rot , the dipole rotation correlation factor [23] for l = 1, and it equals unity for all other l. [14], compared to the experimental oxygen-oxygen radial distribution function gOO(r) [25]. The left panels show the bound charge (+ red, − blue) and electron density (green).…”

“…This sensitivity imposes extremely stringent restrictions on the statistical noise in the DMC electron density, rendering self-consistent solvated DMC calculations impractical. A scheme correct to first order that combines a solvated [29][30][31] and the linear and nonlinear solvation models from [14]. density-functional calculation with a DMC calculation in an external potential provides reasonable accuracy without calculating DMC electron densities [17].…”