Wannier-function-based constrained DFT with nonorthogonality-correcting Pulay forces in application to the reorganization effects in graphene-adsorbed pentacene

Roychoudhury, Subhayan; O’Regan, David D.; Sanvito, Stefano

doi:10.1103/physrevb.97.205120

Cited by 6 publications

(7 citation statements)

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“…We note, once again, that orbital-based Mulliken and Löwdin population analysis is far more economicalin terms of sheer speed by about 1 order of magnitudeto achieve as compared to the density-based Bader approach, but we will now show that Mulliken and Löwdin still yield chemically meaningful results when Bader’s charge analysis reaches its limits, for example, in the case of complex nanoporous compounds of amorphous nature. Because Mulliken population-based non-orthogonalized basis sets are not bound between 0 and 2 for a single orbital, a problem usually considered negligible, , a basis set transformation is needed. , This behavior can therefore be solved using Löwdin’s symmetric orthogonalization. , Hence, we will mainly discuss Löwdin charges in this work.…”

Section: Resultsmentioning

confidence: 99%

First-Principles Plane-Wave-Based Exploration of Cathode and Anode Materials for Li- and Na-Ion Batteries Involving Complex Nitrogen-Based Anions

et al. 2022

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We present a first-principles study based on plane-wave derived Löwdin population analysis and other local bonding descriptors to investigate cathode and anode materials for lithium and sodium ion batteries, with a special emphasis on complex nitrogen chemistry. By comparing the Löwdin charges of commonly used electrode materials to other phases such as salts of dicyanamide and nanoporous carbon-based compounds, new conclusions of an improved intercalation behavior of the latter are derived. In addition, we explore the stability of the dicyanamide salts upon Li and Na removal, some of them resulting in dimerized structures. In particular, having a look at the different kinds of bonds and the corresponding covalency indicators reveals insights into the bonding changes during dimerization. Considering the astonishing thermal stability of metal dicyanamide salts, which are solid at room temperature, their electrochemical activity as well as non-toxicity of alkali metal-based compounds, these materials are potential alternatives to commercially available electrodes, particularly as they show some flexibility in exhibiting anodic and cathodic behavior and allow for transition metal-free cathode materials. This material is available free of charge via the Internet at http://pubs.acs.org.

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Section: Resultsmentioning

confidence: 99%

First-Principles Plane-Wave-Based Exploration of Cathode and Anode Materials for Li- and Na-Ion Batteries Involving Complex Nitrogen-Based Anions

et al. 2022

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“…The linear-scaling first-principles code ONETEP 54 , within which we have implemented the XDFT formalism, variationally optimizes a minimal set of localized, non-orthonormal generalized Wannier Functions (NGWF), expanded in terms of psinc functions 55,56 , to minimize the total energy. ONETEP is equipped with an automated conjugate-gradients method for optimizing the cDFT (or XDFT) Lagrange multiplier 45,57,58 . We have used this, together with the Perdew-Burke-Ernzerhof (PBE) XC functional 59 to calculate the lowest singlet excitation energies of the 28 closed-shell organic molecules contained in the wellknown Thiel set 60 .…”

Section: Methodological Detailsmentioning

confidence: 99%

Neutral excitation density-functional theory: an efficient and variational first-principles method for simulating neutral excitations in molecules

Roychoudhury

Sanvito

O’Regan

2020

Sci Rep

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We introduce neutral excitation density-functional theory (XDFT), a computationally light, generally applicable, first-principles technique for calculating neutral electronic excitations. The concept is to generalise constrained density functional theory to free it from any assumptions about the spatial confinement of electrons and holes, but to maintain all the advantages of a variational method. The task of calculating the lowest excited state of a given symmetry is thereby simplified to one of performing a simple, low-cost sequence of coupled DFT calculations. We demonstrate the efficacy of the method by calculating the lowest single-particle singlet and triplet excitation energies in the wellknown Thiel molecular test set, with results which are in good agreement with linear-response timedependent density functional theory (LR-TDDFT). Furthermore, we show that XDFT can successfully capture two-electron excitations, in principle, offering a flexible approach to target specific effects beyond state-of-the-art adiabatic-kernel LR-TDDFT. Overall the method makes optical gaps and electron-hole binding energies readily accessible at a computational cost and scaling comparable to that of standard density functional theory. Owing to its multiple qualities beneficial to high-throughput studies where the optical gap is of particular interest; namely broad applicability, low computational demand, and ease of implementation and automation, XDFT presents as a viable candidate for research within materials discovery and informatics frameworks. The first-principles calculation of the excited-state energies of quantum systems holds crucial importance for the study of solar cells 1 , organic light emitting diodes 2 , and chromophores in biological systems 3 , to name but a few. With some exceptions, density-functional theory (DFT), the primary ab initio workhorse for computing ground state properties 4,5 , typically falls short on such tasks, although efforts are underway to extend the foundation of DFT to excited states 6-11. The most commonly used first-principles method for calculating excitation energies, at least of finite systems, is linear-response time-dependent density functional theory (LR-TDDFT) 12-14. However, LR-TDDFT has two significant limitations: its computational cost, which severely limits the size of the systems that it can be used to investigate 15 , and its inability to treat double (two-electron) or higher-order excitations within adiabatic approximations to the exchange-correlation (XC) kernel 16-18. Such multi-particle excitations and indeed inter-conversions between excitation types are of considerable interest, not alone on fundamental grounds, but for example in the computational development of photovoltaic materials that intrinsically overcome the Shockley-Queisser limit. Often, it is the lowest excitation energy of a given symmetry that is of principal interest, as this can be used to calculate the electron-hole binding energy. In such cases, state-of-the-art methods that rely on the coupling of ...

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“…Maximization of W with respect to Vc determines the Vc needed to enforce the targeted electronic occupation (Nc) in the cDFT-subspace. 103,119 Atomic forces can then be calculated, 100,123 allowing geometry optimization and molecular dynamics (MD) simulations. The cDFT implementation in ONETEP rests on the use of non-orthogonal, atom-centered projectors (|φn⟩) to calculate the electronic occupation of the given cDFT-subspace, needed in Eq.…”

Section: Constrained Density Functional Theorymentioning

confidence: 99%

“…cDFT in ONETEP has been applied to photovoltaic materials, 124,125 to interfaces in graphene-based composite materials, 123 and to the limitations of cDFT in constraining SIE-free solutions in standard DFT exchange-correlation functionals. 110 Going forward, we expect applications of cDFT to large-scale systems (e.g., biomolecules, nanoparticles, nanotubes, etc.)…”

Section: Constrained Density Functional Theorymentioning

confidence: 99%

The ONETEP linear-scaling density functional theory program

Prentice

Aarons

Womack

et al. 2020

The Journal of Chemical Physics

121

104

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We present an overview of the ONETEP program for linear-scaling density functional theory (DFT) calculations with large basis set (planewave) accuracy on parallel computers. The DFT energy is computed from the density matrix, which is constructed from spatially localized orbitals we call Non-orthogonal Generalized Wannier Functions (NGWFs), expressed in terms of periodic sinc (psinc) functions. During the calculation, both the density matrix and the NGWFs are optimized with localization constraints. By taking advantage of localization, ONETEP is able to perform calculations including thousands of atoms with computational effort, which scales linearly with the number or atoms. The code has a large and diverse range of capabilities, explored in this paper, including different boundary conditions, various exchangecorrelation functionals (with and without exact exchange), finite electronic temperature methods for metallic systems, methods for strongly correlated systems, molecular dynamics, vibrational calculations, time-dependent DFT, electronic transport, core loss spectroscopy, implicit solvation, quantum mechanical (QM)/molecular mechanical and QM-in-QM embedding, density of states calculations, distributed multipole analysis, and methods for partitioning charges and interactions between fragments. Calculations with ONETEP provide unique insights into large and complex systems that require an accurate atomic-level description, ranging from biomolecular to chemical, to materials, and to physical problems, as we show with a small selection of illustrative examples. ONETEP has always aimed to be at the cutting edge of method and software developments, and it serves as a platform for developing new methods of electronic structure simulation. We therefore conclude by describing some of the challenges and directions for its future developments and applications.

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Wannier-function-based constrained DFT with nonorthogonality-correcting Pulay forces in application to the reorganization effects in graphene-adsorbed pentacene

Cited by 6 publications

References 84 publications

First-Principles Plane-Wave-Based Exploration of Cathode and Anode Materials for Li- and Na-Ion Batteries Involving Complex Nitrogen-Based Anions

First-Principles Plane-Wave-Based Exploration of Cathode and Anode Materials for Li- and Na-Ion Batteries Involving Complex Nitrogen-Based Anions

Neutral excitation density-functional theory: an efficient and variational first-principles method for simulating neutral excitations in molecules

The ONETEP linear-scaling density functional theory program

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