Publications

A two-pronged approach to the cuprate pseudogap: A comparison of mode-coupling and first-principles (SCAN) results

A first- principles study of insulating La 2 CuO and its transition to the metallic state with Sr-doping

Effect of the orbital-overlap dependence in the Meta Generalized Gradient Approximation

Bonding in the metallic molecular solid <i>α</i>-Gallium

Solid, liquid and alloyed phases of gallium play a role in a variety of important technological applications. While many of the gallium phases involved in these applications are metallic, some have been proposed or are known to contain covalently bound Ga dimers. Thus, understanding the nature of bonding in Ga is crucial to the development of Ga-based materials. The solid phase of gallium at ambient conditions, <i>α</i>-Ga, is metallic and composed of molecular dimers, and can serve as a testing ground for studying gallium bonding with electronic structure calculations. We use density functional theory-based molecular dynamics simulations in conjunction with maximally localised Wannier functions to examine the nature of chemical bonding in <i>α</i>-Ga. We propose a geometric criterion for defining various bonding environments, which enables the quantification of covalent and weak bonds in solid gallium. We additionally connect the bonding structure of <i>α</i>-Ga to its phonon density of states and discuss similarities and differences with diatomic halogen crystals.

Simple physical picture of the Overhauser screened electron-electron interaction

As shown by Overhauser and others, the pair-distribution function $g(r)$ of a many-electron system may be found by solving a two-electron scattering problem with an effective screened electron-electron repulsion $V(r).$ We propose a simple physical picture in which this screened repulsion is the ``dressed-dressed'' interaction between two neutral objects, each an electron surrounded by its full-coupling exchange-correlation hole. For the effective interaction between two electrons of antiparallel spin in a high-density uniform electron gas of arbitrary spin polarization, we confirm that this picture is qualitatively correct. In contrast, the ``bare-dressed'' interaction is too repulsive, and does not have the expected symmetry ${V}_{\ensuremath{\uparrow}\ensuremath{\downarrow}}{(r)=V}_{\ensuremath{\downarrow}\ensuremath{\uparrow}}(r).$ The simple original Overhauser model interaction, independent of the relative spin polarization $\ensuremath{\zeta},$ does not capture the $\ensuremath{\zeta}$ dependence of the correlation contribution to $g(r=0).$

Climbing the ladder of density functional approximations

Locality of the Ontop Exchange-Correlation Hole Density

Exchange and Correlation In Atoms, Molecules, And Solids: The Density Functional Picture

Communication: Near-locality of exchange and correlation density functionals for 1- and 2-electron systems

© 2016 Author(s). The uniform electron gas and the hydrogen atom play fundamental roles in condensed matter physics and quantum chemistry. The former has an infinite number of electrons uniformly distributed over the neutralizing positively charged background, and the latter only one electron bound to the proton. The uniform electron gas was used to derive the local spin density approximation to the exchange-correlation functional that undergirds the development of the Kohn-Sham density functional theory. We show here that the ground-state exchange-correlation energies of the hydrogen atom and many other 1- and 2-electron systems are modeled surprisingly well by a different local spin density approximation (LSDA0). LSDA0 is constructed to satisfy exact constraints but agrees surprisingly well with the exact results for a uniform two-electron density in a finite, curved three-dimensional space. We also apply LSDA0 to excited or noded 1-electron densities, where it works less well. Furthermore, we show that the localization of the exact exchange hole for a 1- or 2-electron ground state can be measured by the ratio of the exact exchange energy to its optimal lower bound.

Properties of real metallic surfaces: Effects of density functional semilocality and van der Waals nonlocality

We have computed the surface energies, work functions, and interlayer surface relaxations of clean (111), (110), and (100) surfaces of Al, Cu, Ru, Rh, Pd, Ag, Pt, and Au. Many of these metallic surfaces have technological or catalytic applications. We compare experimental reference values to those of the local density approximation (LDA), the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA), the PBEsol (PBE for solids) GGA, the SCAN meta-GGA, and SCAN+rVV10 (SCAN with a long-range van der Waals or vdW correction). The closest agreement with uncertain experimental values is achieved by the simplest density functional (LDA) and by the most sophisticated general-purpose one (SCAN+rVV10). The long-range vdW interaction increases the surface energies by about 10%, and the work functions by about 1%. LDA works for metal surfaces through a stronger-than-usual error cancellation. PBE yields the most-underestimated and presumably least accurate surface energies and work functions. Surface energies within the random phase approximation (RPA) are also reported. Interlayer relaxations from different functionals are in reasonable agreement with one another, and usually with experiment.

Simplified Generalized Gradient Approximation

Erratum: Workhorse Semilocal Density Functional for Condensed Matter Physics and Quantum Chemistry [Phys. Rev. Lett.<b>103</b>, 026403 (2009)]

Received 5 April 2011DOI:https://doi.org/10.1103/PhysRevLett.106.179902© 2011 American Physical Society

Kohn-Sham exact-exchange for atoms and clusters

Transition Metal Carbo‐Chalcogenide “TMCC:” A New Family of 2D Materials (Adv. Mater. 26/2022)

Transition Metal Carbo-Chalcogenides In article number 2200574, Michael Naguib and co-workers report on the synthesis of 2D transition metal carbo-chalcogenides (TMCCs) by exfoliating their bulk layered counterparts (e.g., Nb2S2C and Ta2S2C) through electrochemical Li-ion intercalation followed by agitation in water. 2D TMCCs combine the surface of 2D TM dichalcogenides (TMDCs) and the core of 2D TM carbides (MXenes) offering unique characteristics of both TMDCs and MXenes.

Unitarily Invariant Self-Interaction Corrections to the Uniform Electron Gas

Accurate first-principles description of the antiferromagnetic state of La 2 CuO 4

Orbital shifts: An easy way to calculate the exact Kohn-Sham exchange potential

Meta-generalized gradient approximation for the exchange-correlation hole with an application to the jellium surface energy

We propose a model for the angle- and system-averaged exchange-correlation hole of a many-electron system. This hole analyzes the exchange-correlation energy into contributions of various distances $u$ from an electron. The model is ``reverse-engineered'' (derived from and not used to derive a density functional). It satisfies known exact hole constraints, including ones that can only be satisfied by a meta-generalized gradient approximation or meta-GGA. It incorporates the exchange-correlation energy density of the Tao-Perdew-Staroverov-Scuseria (TPSS) nonempirical meta-GGA. The hole model is tested for atoms and applied to jellium surfaces. The Fourier transform $(u\ensuremath{\rightarrow}k)$ of the hole is needed for wave-vector interpolation of the jellium surface energy from an exact small-$k$ or large-$u$ asymptote. We find essentially the same surface energies (close to the uncorrected TPSS values) whether we apply the wave-vector interpolation correction to the local spin density approximation, the GGA or the meta-GGA. These and other considerations suggest that these surface energies are accurate. Moreover, we find that the uncorrected TPSS surface energies have a realistic wave-vector analysis. Our TPSS hole model can be used to build the hole model for a TPSS-based global hybrid functional, or for a hyper-GGA that uses full exact exchange.