scholarly journals Looking Beyond Adsorption Energies to Understand Interactions at Surface Using Machine Learning

2021 ◽  
Author(s):  
Sheena Agarwal ◽  
Kavita Joshi
Keyword(s):  
Machine Learning ◽  
Small Molecules ◽  
Density Functional ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Full Picture ◽  
Adsorption Energies ◽  
Face Centered

Abstract<br>Identifying factors that influence interactions at the surface is still an active area of research. In this study, we present the importance of analyzing bondlength activation, while interpreting Density Functional Theory (DFT) results, as yet another crucial indicator for catalytic activity. We studied the<br>adsorption of small molecules, such as O 2 , N 2 , CO, and CO 2 , on seven face-centered cubic (fcc) transition metal surfaces (M = Ag, Au, Cu, Ir, Rh, Pt, and Pd) and their commonly studied facets (100, 110, and 111). Through our DFT investigations, we highlight the absence of linear correlation between adsorption energies (E ads ) and bondlength activation (BL act ). Our study indicates the importance of evaluating both to develop a better understanding of adsorption at surfaces. We also developed a Machine Learning (ML) model trained on simple periodic table properties to predict both, E ads and BL act . Our ML model gives an accuracy of Mean Absolute Error (MAE) ∼ 0.2 eV for E ads predictions and 0.02 Å for BL act predictions. The systematic study of the ML features<br>that affect E ads and BL act further reinforces the importance of looking beyond adsorption energies to get a full picture of surface interactions with DFT.<br>

scholarly journals Looking Beyond Adsorption Energies to Understand Interactions at Surface Using Machine Learning

2021 ◽  
Author(s):  
Sheena Agarwal ◽  
Kavita Joshi
Keyword(s):  
Machine Learning ◽  
Small Molecules ◽  
Density Functional ◽  
Mean Absolute Error ◽  
Absolute Error ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Full Picture ◽  
Adsorption Energies ◽  
Face Centered

Abstract<br>Identifying factors that influence interactions at the surface is still an active area of research. In this study, we present the importance of analyzing bondlength activation, while interpreting Density Functional Theory (DFT) results, as yet another crucial indicator for catalytic activity. We studied the<br>adsorption of small molecules, such as O 2 , N 2 , CO, and CO 2 , on seven face-centered cubic (fcc) transition metal surfaces (M = Ag, Au, Cu, Ir, Rh, Pt, and Pd) and their commonly studied facets (100, 110, and 111). Through our DFT investigations, we highlight the absence of linear correlation between adsorption energies (E ads ) and bondlength activation (BL act ). Our study indicates the importance of evaluating both to develop a better understanding of adsorption at surfaces. We also developed a Machine Learning (ML) model trained on simple periodic table properties to predict both, E ads and BL act . Our ML model gives an accuracy of Mean Absolute Error (MAE) ∼ 0.2 eV for E ads predictions and 0.02 Å for BL act predictions. The systematic study of the ML features<br>that affect E ads and BL act further reinforces the importance of looking beyond adsorption energies to get a full picture of surface interactions with DFT.<br>

scholarly journals Influence of Si Atoms Insertion on the Formation of the Ti-Si-N Composite by DFT Simulation

2016 ◽  
Vol 12 (23) ◽  
pp. 11-23
Author(s):  
Juan Manuel Gonzalez ◽  
Johans Steeven Restrepo ◽  
Carolina Ortega Portilla ◽  
Alexander Ruden Muñoz ◽  
Federico Sequeda Osorio
Keyword(s):  
Density Functional ◽  
Amorphous Matrix ◽  
Bond Formation ◽  
Crystalline Lattice ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Dft Simulation ◽  
Face Centered ◽  
Nano Grains ◽  
Fcc Structure

Using Density Functional Theory (DFT) SiN and TiN structures were simulated, in order to study the influence of the silicon atoms insertion in the TiN lattice placed on interstitial and substitutional positions in a face centered cubic (FCC) crystalline lattice. Results showed that the SiN - FCC structure is pseudo-stable; meanwhile the tetragonal structure is stable with ceramic behavior. The TiN - FCC structure is stable with ceramic behavior similar to SiN - Tetragonal. 21% silicon atoms insertion in interstitial positions showed high induced deformation, high polarization and Si - N bond formation, indication an amorphous transition that could lead to the production of a material composed from TiN grains or nano-grains embedded in a Si - N amorphous matrix. When including 21% of silicon atoms, substituting titanium atoms, the distribution showed higher stability that could lead to the formation of different phases of the stoichiometric Ti1 -x SixNy compound.

Electric-Field Assisted Modulation of Surface Thermochemistry

2020 ◽  
Author(s):  
Manish Shetty ◽  
Matthew Ardagh ◽  
Yutong Pang ◽  
Omar Abdelrahman ◽  
Paul Dauenhauer
Keyword(s):  
Electric Field ◽  
Density Functional ◽  
Surface Composition ◽  
Absolute Error ◽  
Catalyst Design ◽  
Zero Field ◽  
Product Selectivity ◽  
Functional Theory ◽  
Adsorption Energies ◽  
And Control

<p>Conventional catalyst design has enhanced reactivity and product selectivity through control of surface thermochemistry by tunable surface composition and the surrounding environment (e.g., pore structure). In this work, the prospect for electric field towards controlling product selectivity and reaction networks on the Pt(111) surface was evaluated with periodic density functional theory (DFT) calculations in concert with machine learning (ML) algorithms. Linear scaling relationships (LSRs) for adsorption energies of surface species in electric field were shown to: (i) be distinct as compared to zero-field LSRs across metals, and (ii) linearly correlate with adsorption energies of H* rather than the binding element. The slope of LSRs linearly correlated with the zero-field dipole moment. A random forest ML regression algorithm predicted field-dependent adsorption energies with a mean absolute error (0.12 eV) comparable to DFT. Overall, this study identifies the path forward for electric field-assisted catalysis, specifically towards catalyst poisoning, product selectivity, and control of reaction pathways.</p>

Pressure induced phase transitions in AmCm alloy

2005 ◽  
Vol 893 ◽  
Author(s):  
Sa Li ◽  
Rajeev Ahuja ◽  
Borje Johansson
Keyword(s):  
Density Functional ◽  
Alloy System ◽  
Face Centered Cubic ◽  
Generalized Gradient ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Face ◽  
Face Centered ◽  
Good Agreement

AbstractWe have studied the crystal structure of the AmCm binary alloy under high pressure by means of first-principles self-consistent total-energy calculations using the generalized gradient approximation (GGA) for the density functional theory (DFT). The virtual crystal approximation (VCA) is used for the description of the alloy system. In the present study, we investigated the double hexagonal (P63/mmc) structure, the face centered cubic (Fm3m) structure, the face-centered orthorhombic (Fddd) structure and the primitive orthorhombic (Pnma) structure for the AmCm alloy. Antiferromagnetic calculations have been compared with ferromagnetic calculations for all these phases. Our results are in general good agreement with recent experiment performed by Lindbaum et al. [J. Phys.: Condens. Matter. 15, S2297 (2003)].

Symmetry reduction of δ-plutonium: an electronic-structure effect

2005 ◽  
Vol 893 ◽  
Author(s):  
Kevin T. Moore ◽  
Per Söderlind ◽  
Adam J. Schwartz ◽  
David Laughlin
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Monoclinic Space Group ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Space Group ◽  
Bond Strengths ◽  
Reduced Space ◽  
Face Centered

AbstractUsing first-principles density-functional theory calculations, we show that the anomalously large anisotropy of δ-plutonium is a consequence of greatly varying bond-strengths between the 12 nearest neighbors. Employing the calculated bond strengths, we expand the tenants of classical crystallography by incorporating anisotropy of chemical bonds, which yields a structure with the monoclinic space group Cm for δ-plutonium rather than face-centered cubic Fm3m. The reduced space group for δ-plutonium enlightens why the ground state of the metal is monoclinic, why distortions of the metal are viable, and has considerable implications for the behavior of the material as it ages. These results illustrate how an expansion of classical crystallography that accounts for anisotropic electronic structure can explain complicated materials in a novel way.

Theoretical Investigation of Carbon Atom Adsorption and Diffusion on the Surfaces of Cu

2014 ◽  
Vol 1082 ◽  
pp. 475-479
Author(s):  
Liang Qiao ◽  
Shu Jie Liu ◽  
Xiao Ying Hu ◽  
Li Li Wang ◽  
Dong Mei Bi
Keyword(s):  
Carbon Atom ◽  
First Principles ◽  
Density Functional ◽  
Energy Difference ◽  
Face Centered Cubic ◽  
Functional Theory ◽  
Hexagonal Close Packed ◽  
Adsorbed Carbon ◽  
Face Centered ◽  
And Diffusion

The adsorption and diffusion of carbon atom on Cu (111) and (100) surfaces have been investigated based on first-principles density-functional theory. For Cu (111) surface, the hexagonal close-packed and face-centered cubic sites are the most stable sites with little energy difference in the adsorption energy. For Cu (100) surface, the hollow site is the most stable. There is charge transfer from Cu surface to the adsorbed carbon atom. Moreover, the diffusions of carbon atom on Cu surfaces have been investigated, and the results show that the diffusion of carbon atom prefers to happen on Cu (111) surface.

scholarly journals Theoretical confirmation of Ga-stabilized anti-ferromagnetism in plutonium metal

2014 ◽  
Vol 1683 ◽  
Author(s):  
Per Söderlind ◽  
Alex Landa
Keyword(s):  
Density Functional ◽  
Magnetic Measurements ◽  
Theory Model ◽  
Face Centered Cubic ◽  
Mechanical Instability ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
The Face ◽  
Face Centered ◽  
Plutonium Metal

ABSTRACTThe density-functional-theory model for plutonium metal is shown to be consistent with recent magnetic measurements that suggest anti-ferromagnetism in Pu-Ga alloys at low temperatures. The theoretical model predicts a stabilization of the face-centered-cubic (fcc, δ) form of plutonium in an anti-ferromagnetic configuration when alloyed with gallium. The ordered magnetic phase occurs because Ga removes the mechanical instability that exists for unalloyed δ-Pu. The cause of the Ga-induced stabilization is a combination of a lowering of the band (kinetic) and electrostatic (Coulomb) energies for the cubic relative to the tetragonal phase.

Electric-Field Assisted Modulation of Surface Thermochemistry

2020 ◽  
Author(s):  
Manish Shetty ◽  
Matthew Ardagh ◽  
Yutong Pang ◽  
Omar Abdelrahman ◽  
Paul Dauenhauer
Keyword(s):  
Electric Field ◽  
Density Functional ◽  
Surface Composition ◽  
Absolute Error ◽  
Catalyst Design ◽  
Zero Field ◽  
Product Selectivity ◽  
Functional Theory ◽  
Adsorption Energies ◽  
And Control

<p>Conventional catalyst design has enhanced reactivity and product selectivity through control of surface thermochemistry by tunable surface composition and the surrounding environment (e.g., pore structure). In this work, the prospect for electric field towards controlling product selectivity and reaction networks on the Pt(111) surface was evaluated with periodic density functional theory (DFT) calculations in concert with machine learning (ML) algorithms. Linear scaling relationships (LSRs) for adsorption energies of surface species in electric field were shown to: (i) be distinct as compared to zero-field LSRs across metals, and (ii) linearly correlate with adsorption energies of H* rather than the binding element. The slope of LSRs linearly correlated with the zero-field dipole moment. A random forest ML regression algorithm predicted field-dependent adsorption energies with a mean absolute error (0.12 eV) comparable to DFT. Overall, this study identifies the path forward for electric field-assisted catalysis, specifically towards catalyst poisoning, product selectivity, and control of reaction pathways.</p>

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