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Publications

Density-functional fluctuation theory of crowds

Cornell Affiliated Author(s)
Author
J.F. Méndez-Valderrama
Y.A. Kinkhabwala
J. Silver
Itai Cohen
Tomas Arias
Abstract

A primary goal of collective population behavior studies is to determine the rules governing crowd distributions in order to predict future behaviors in new environments. Current top-down modeling approaches describe, instead of predict, specific emergent behaviors, whereas bottom-up approaches must postulate, instead of directly determine, rules for individual behaviors. Here, we employ classical density functional theory (DFT) to quantify, directly from observations of local crowd density, the rules that predict mass behaviors under new circumstances.

Journal
Nature Communications
Date Published
Funding Source
W911NF-16-1-0433
DGE-1650441
D71TW010433
Army-ARO W911NF-16-1-0433
Group (Lab)
Itai Cohen Group
Tomas Arias Group

Direct visualization of sulfur cathodes: New insights into Li-S batteries via operando X-ray based methods

Cornell Affiliated Author(s)
Author
S.-H. Yu
X. Huang
K. Schwarz
R. Huang
Tomas Arias
J.D. Brock
H.D. Abruña
Abstract

As the need for the development of "beyond lithium" ion battery technologies continues unabated, lithium sulfur batteries have attracted widespread attention due to their very high theoretical energy density of 2600 W h kg-1. However, despite much effort, the detailed reaction mechanism remains poorly understood. In this study, we have combined operando X-ray diffraction and X-ray microscopy along with X-ray tomography, to visualize the evolution of both the morphology and crystal structure of the materials during the entire battery cycling (discharging/charging) process.

Journal
Energy and Environmental Science
Date Published
Funding Source
DMR-1332208
2015R1A6A3A03020354
Group (Lab)
Tomas Arias Group

Designing solid-liquid interphases for sodium batteries

Cornell Affiliated Author(s)
Author
S. Choudhury
S. Wei
Y. Ozhabes
D. Gunceler
M.J. Zachman
Z. Tu
J.H. Shin
P. Nath
A. Agrawal
L.F. Kourkoutis
Tomas Arias
L.A. Archer
Abstract

Secondary batteries based on earth-abundant sodium metal anodes are desirable for both stationary and portable electrical energy storage. Room-temperature sodium metal batteries are impractical today because morphological instability during recharge drives rough, dendritic electrodeposition. Chemical instability of liquid electrolytes also leads to premature cell failure as a result of parasitic reactions with the anode.

Journal
Nature Communications
Date Published
Funding Source
1654596
DMR-1654596
-AR0000750
KUS-C1-018-02
Group (Lab)
Tomas Arias Group

Surface analysis of features seen on Nb3Sn sample coupons grown by vapour diffusion

Cornell Affiliated Author(s)
Author
D.L. Hall
Tomas Arias
P. Cueva
M. Liepe
J.T. Maniscalco
D.A. Muller
R.D. Porter
N. Sitaraman
Abstract

As a high-kappa superconductor with a coherence length of 7 nm, the superconductor Nb3Sn is highly susceptible to material features at the sub-micron scale. For niobium surfaces coated with a thin layer of Nb3Sn using the vapour diffusion method, the polycrystalline nature of the film grown lends to the possibility that performance-degrading nonuniformities may develop. In particular, regions of insufficiently thick coating and tin-depletion have been seen to occur in sample coupons.

Conference Name
.
Date Published
Funding Source
PHY-1549132
DE-SC0008431
DMR-1120296
Group (Lab)
Tomas Arias Group

Grand canonical electronic density-functional theory: Algorithms and applications to electrochemistry

Cornell Affiliated Author(s)
Author
R. Sundararaman
W.A. Goddard III
Tomas Arias
Abstract

First-principles calculations combining density-functional theory and continuum solvation models enable realistic theoretical modeling and design of electrochemical systems. When a reaction proceeds in such systems, the number of electrons in the portion of the system treated quantum mechanically changes continuously, with a balancing charge appearing in the continuum electrolyte. A grand-canonical ensemble of electrons at a chemical potential set by the electrode potential is therefore the ideal description of such systems that directly mimics the experimental condition.

Journal
Journal of Chemical Physics
Date Published
Funding Source
DE-SC0004993
DE-AC02-05CH11231
DE-SC0001086
Group (Lab)
Tomas Arias Group

Towards a generalized iso-density continuum model for molecular solvents in plane-wave DFT

Cornell Affiliated Author(s)
Author
D. Gunceler
Tomas Arias
Abstract

Implicit electron-density solvation models offer a computationally efficient solution to the problem of calculating thermodynamic quantities of solvated systems from first-principles quantum mechanics. However, despite much recent interest in such models, to date the applicability of such models in the plane-wave context to non-aqueous solvents has been limited because the determination of the model parameters requires fitting to a large database of experimental solvation energies for each new solvent considered.

Journal
Modelling and Simulation in Materials Science and Engineering
Date Published
Group (Lab)
Tomas Arias Group

JDFTx: Software for joint density-functional theory

Cornell Affiliated Author(s)
Author
R. Sundararaman
K. Letchworth-Weaver
K.A. Schwarz
D. Gunceler
Y. Ozhabes
Tomas Arias
Abstract

Density-functional theory (DFT) has revolutionized computational prediction of atomic-scale properties from first principles in physics, chemistry and materials science. Continuing development of new methods is necessary for accurate predictions of new classes of materials and properties, and for connecting to nano- and mesoscale properties using coarse-grained theories. JDFTx is a fully-featured open-source electronic DFT software designed specifically to facilitate rapid development of new theories, models and algorithms.

Journal
SoftwareX
Date Published
Funding Source
DE-SC0004993
2013–2016
DE-SC0001086
Group (Lab)
Tomas Arias Group

Structure of the Photo-catalytically Active Surface of SrTiO3

Cornell Affiliated Author(s)
Author
M. Plaza
X. Huang
J.Y.P. Ko
M. Shen
B.H. Simpson
J. Rodríguez-López
N.L. Ritzert
K. Letchworth-Weaver
D. Gunceler
D.G. Schlom
Tomas Arias
J.D. Brock
H.D. Abruña
Abstract

A major goal of energy research is to use visible light to cleave water directly, without an applied voltage, into hydrogen and oxygen. Although SrTiO3 requires ultraviolet light, after four decades, it is still the "gold standard" for the photo-catalytic splitting of water. It is chemically robust and can carry out both hydrogen and oxygen evolution reactions without an applied bias.

Journal
Journal of the American Chemical Society
Date Published
Funding Source
DMR-0936384
0936384
DE-SC0001086
Group (Lab)
Tomas Arias Group

Computationally efficient dielectric calculations of molecular crystals

Cornell Affiliated Author(s)
Author
K.A. Schwarz
R. Sundararaman
Tomas Arias
Abstract

The microscopic dielectric response is a key quantity for electronic materials such as organic semiconductors. Calculations of this response for molecular crystals are currently either expensive or rely on extreme simplifications such as multipole expansions which lack microscopic detail. We present an alternate approach using a microscopic analogue of the Clausius-Mossotti equation, which constructs the dielectric response of a crystal from an eigenvalue decomposition of the dielectric response of individual molecules.

Journal
Journal of Chemical Physics
Date Published
Group (Lab)
Tomas Arias Group

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

Cornell Affiliated Author(s)
Author
R. Sundararaman
K.A. Schwarz
K. Letchworth-Weaver
Tomas Arias
Abstract

Continuum solvation models enable electronic structure calculations of systems in liquid environments, but because of the large number of empirical parameters, they are limited to the class of systems in their fit set (typically organic molecules). Here, we derive a solvation model with no empirical parameters for the dielectric response by taking the linear response limit of a classical density functional for molecular liquids.

Journal
Journal of Chemical Physics
Date Published
Group (Lab)
Tomas Arias Group