scholarly journals Optical Activity of Metal Nanoclusters Deposited on Regular and Doped Oxide Supports from First-Principles Simulations

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6961
Author(s):  
Luca Sementa ◽  
Mauro Stener ◽  
Alessandro Fortunelli
Keyword(s):  
Transition Metal ◽  
Oxygen Vacancy ◽  
Density Functional ◽  
Computational Study ◽  
Metal Nanoclusters ◽  
Oxide Supports ◽  
Oxide Support ◽  
Cation Framework ◽  
Localized Excitations ◽  
Magnesium Cation

We report a computational study and analysis of the optical absorption processes of Ag20 and Au20 clusters deposited on the magnesium oxide (100) facet, both regular and including point defects. Ag20 and Au20 are taken as models of metal nanoparticles and their plasmonic response, MgO as a model of a simple oxide support. We consider oxide defects both on the oxygen anion framework (i.e., a neutral oxygen vacancy) and in the magnesium cation framework (i.e., replacing Mg++ with a transition metal: Cu++ or Co++). We relax the clusters’ geometries via Density-Functional Theory (DFT) and calculate the photo-absorption spectra via Time-Dependent DFT (TDDFT) simulations on the relaxed geometries. We find that the substrate/cluster interaction induces a broadening and a red-shift of the excited states of the clusters, phenomena that are enhanced by the presence of an oxygen vacancy and its localized excitations. The presence of a transition-metal dopant does not qualitatively affect the spectral profile. However, when it lies next to an oxygen vacancy for Ag20, it can strongly enhance the component of the cluster excitations perpendicular to the surface, thus favoring charge injection.

A computational study of hydrogen doping induced metal-to-insulator transition in CaFeO3, SrFeO3, BaFeO3 and SmMnO3

2019 ◽  
Vol 21 (45) ◽  
pp. 25397-25405
Author(s):  
Shukai Yao ◽  
Pilsun Yoo ◽  
Peilin Liao
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
First Principles ◽  
Density Functional ◽  
Computational Study ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Hydrogen Doping ◽  
Gap Opening ◽  
Metal To Insulator Transition

First principles density functional theory calculations were performed to identify transition metal perovskites CaFeO3, SrFeO3, BaFeO3 and SmMnO3 as promising candidates with large band gap opening upon hydrogen doping.

The crystal structure and phase stability of the zeta phase in the group VB transition metal carbides: a computational investigation

2019 ◽  
Vol 75 (5) ◽  
pp. 870-879 ◽  
Author(s):  
Christopher R. Weinberger ◽  
Gregory B. Thompson
Keyword(s):  
Crystal Structure ◽  
Transition Metal ◽  
Phase Stability ◽  
Density Functional ◽  
Computational Study ◽  
Equilibrium Phase ◽  
Tantalum Carbide ◽  
High Fracture Toughness ◽  
Metal Carbides ◽  
Transition Metal Carbides

The crystal structure and composition of the zeta phase in the group VB transition metal carbides are not completely understood despite decades of experimental studies. As such, the phase rarely appears on phase diagrams of the group VB transition metal carbides. There is currently renewed interest in this phase, as tantalum carbide composites exhibit high fracture toughness in the presence of this phase. This work extends the initial computational study using density functional theory of the phase stability of the zeta phase in the tantalum carbide system, where the tantalum carbide zeta-phase crystal structure and stability were determined, to the niobium and vanadium carbides. It is shown that the zeta phases in the three systems share the same crystal structure and it is an equilibrium phase at low temperatures. The carbon atom ordering in the three different phases is explored and it is demonstrated that the zeta phase in the tantalum carbides prefers to order carbon atoms differently than in the niobium and vanadium carbide zeta phases. Finally, the properties of this crystal are computed, including elastic constants, electronic densities of states and phonon dispersion curves, to illustrate that this crystal structure is similar to other transition metal carbides.

scholarly journals Computational Screening of Transition Metal /p-block Hybrid Electrocatalysts for CO2 Reduction

2019 ◽  
Author(s):  
Sahithi Ananthaneni ◽  
Rees Rankin
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Computational Study ◽  
Co2 Reduction ◽  
Density Functional Theory Calculations ◽  
Reduction Reaction ◽  
Intermediate Species ◽  
Computational Screening ◽  
Reduction Of Co2 ◽  
Future Work

Among all the pollutants in the atmosphere, CO2 has the highest impact on global warming and with the rising levels of this pollutant, studies on developing various technologies to convert CO2 into carbon neutral fuels and chemicals have become more valuable. In this work, we present a detailed computational study of electrochemical reduction of CO2 reduction (CO2RR) to methane and methanol over different transition metal-p block catalysts using Density Functional Theory calculations. In addition to the catalyst structure, we studied reaction mechanisms using free energy diagrams that explain the product selectivity with respect to the competing hydrogen evolution reaction. Furthermore, we developed scaling relations between all the active C bound intermediate species with ΔG (CO*) and O bound species with ΔG (OH*). The limiting potential lines with ΔG(OH*) as descriptor are much less negative compared to UL lines with ΔG(CO*) as descriptor indicating that catalyst materials following pathways via OH- bound intermediate species require more negative potentials than CO*HCO* and CO2 COOH* steps to convert into products. We developed thermodynamic volcano plots with two descriptors; CO* and OH* binding free energies and determined the best catalyst material among the initially investigated catalyst materials expecting this plot will provide guidance to the future work on improving the activity of transition metal-p block catalysts for this important reduction reaction.<br>

Identification of optimally stable nanocluster geometries via mathematical optimization and density-functional theory

2020 ◽  
Vol 5 (1) ◽  
pp. 232-244 ◽  
Author(s):  
Natalie M. Isenberg ◽  
Michael G. Taylor ◽  
Zihao Yan ◽  
Christopher L. Hanselman ◽  
Giannis Mpourmpakis ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
Dft Calculations ◽  
Density Functional ◽  
Mathematical Optimization ◽  
Metal Nanoclusters ◽  
Functional Theory

A novel methodology combining mathematical optimization with DFT calculations is developed to determine highly cohesive transition metal nanoclusters.

Bis(cyclopentadienyl)dihydrido Mo and W complexes as Lewis bases — A computational study about their adducts with BX3 (X = F, Cl) and Al(CH3)3

2009 ◽  
Vol 87 (10) ◽  
pp. 1406-1414 ◽  
Author(s):  
Mario Amati ◽  
Francesco Lelj
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Computational Study ◽  
Computational Investigation ◽  
Acid Base ◽  
Base Interaction ◽  
Lewis Bases ◽  
Functional Methods ◽  
Acid Base Interaction

A computational investigation about the Lewis acid–base adducts between bases Cp2MH2 (M = Mo, W) and acids BX3 (X = F, Cl) and Al(CH3)3 is presented. Density functional methods based on pure and hybrid correlation-exchange functionals and relativistic corrections based on the zero order relativistic approximation (ZORA) have been applied. A comparison with experimental data has been addressed to give insights about the nature of the acid–base interaction with the aim to evaluate the role of the transition metal in charge donation toward the acid centre. In this respect, the likelihood of proposed criteria for recognizing the presence of transition-metal direct charge donation has been discussed.

scholarly journals Computational Screening of Transition Metal /p-block Hybrid Electrocatalysts for CO2 Reduction

2019 ◽  
Author(s):  
Sahithi Ananthaneni ◽  
Rees Rankin
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Computational Study ◽  
Co2 Reduction ◽  
Density Functional Theory Calculations ◽  
Reduction Reaction ◽  
Intermediate Species ◽  
Computational Screening ◽  
Reduction Of Co2 ◽  
Future Work

Among all the pollutants in the atmosphere, CO2 has the highest impact on global warming and with the rising levels of this pollutant, studies on developing various technologies to convert CO2 into carbon neutral fuels and chemicals have become more valuable. In this work, we present a detailed computational study of electrochemical reduction of CO2 reduction (CO2RR) to methane and methanol over different transition metal-p block catalysts using Density Functional Theory calculations. In addition to the catalyst structure, we studied reaction mechanisms using free energy diagrams that explain the product selectivity with respect to the competing hydrogen evolution reaction. Furthermore, we developed scaling relations between all the active C bound intermediate species with ΔG (CO*) and O bound species with ΔG (OH*). The limiting potential lines with ΔG(OH*) as descriptor are much less negative compared to UL lines with ΔG(CO*) as descriptor indicating that catalyst materials following pathways via OH- bound intermediate species require more negative potentials than CO*HCO* and CO2 COOH* steps to convert into products. We developed thermodynamic volcano plots with two descriptors; CO* and OH* binding free energies and determined the best catalyst material among the initially investigated catalyst materials expecting this plot will provide guidance to the future work on improving the activity of transition metal-p block catalysts for this important reduction reaction.<br>

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