Materials and interfaces containing d(f) electrons are very common in electrochemical energy- and power-storage technologies ranging from (Li-ion) batteries to metal-oxide based supercapacitors. Understanding the atomic factors governing the functioning and degradation of such interfaces is a recognised necessity towards time- and cost-effective development of improved long-term solutions. The experimental challenges in obtaining atom- and time-resolved insight into electrochemical interfaces make accurate Density Functional Theory (DFT) modeling a growingly important tool in fundamental energy storage research. Unfortunately, self-interaction errors in the computationally most advantageous DFT functionals lead to severe accuracy-viability compromises for standard DFT simulation of extended d(f)-electron interface-models.1 These problems can be ameliorated by capitalising on recent advances in linear-scaling DFT simulation2 and subspace-corrected functionals.1Here, based on the self-consistent, tensorially-invariant, subspace representations3 available in the linear-scaling DFT program ONETEP,2 we present a projector-based implementation of the constrained-DFT formalism (cDFT 4), and its use for evaluation of subspace corrections directly from the second derivative of the variationally optimized energy with respect the occupation of symmetry-related subspaces.1 The method is illustrated by exploring the dependence of subspace (+U) corrections on the local environment for two archetypal metal-oxide systems, bulk Li7Ti5O12 and the rutile TiO2(110) surface. We find the U-corrections to be non-negligibly dependent on the chemical surrounding of the subspace, with deviation in the calculated U's ranging from 0.2 eV [TiO2(110)] to up to 0.5 eV [Li7Ti5O12], and affecting electron-polaron relaxation energies in TiO2(110) up to nearly 0.4 eV.These advances open up for straightforward evaluation of subspace-specific corrections in extended (up to a few thousand atoms) models, and more realistic DFT-based simulation of electrochemical interfaces and correlated ion-electron dynamics therein.[1]  Int. J. Quant. Chem. 114 , 14 (2014); [2]  www.onetep.org; [3]  Phys. Rev. B 85, 085107 (2012), and references therein; [4]  Chem. Rev. 112 , 321 (2012).

Subspace-corrected functionals for linear-scaling density functional theory simulation of extended energy storage interfaces

248th National Meeting (2014)

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