scholarly journals Reaction on a Rink: Kondo-Enhanced Heterogeneous Single-atom Catalysis

2021 ◽  
Author(s):  
Xiangyang Li ◽  
Hong Gong ◽  
Qingfeng Zhuang ◽  
Bing Wang ◽  
Xiao Zheng ◽  
...  
Keyword(s):  
Density Functional ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Single Atom ◽  
Spin Interaction ◽  
Free Energy Barrier ◽  
Free Electrons ◽  
Atomic Spin ◽  
Novel Approach ◽  
Metal Support

Boosting the efficiency of heterogeneous single-atom catalysts (SACs) by adjusting the microenvironment of the active atom has recently attracted enormous attention. However, attempts to tune the spin-spin interaction between the SAC and its microenvironment have remained rather scarce. Some interesting questions can be raised, among which a fundamental one is: can the surrounding environment influence the local spin state of an SAC, and if so, can such influence be utilized to enhance the catalytic activity? In this work, we explore such a possibility by investigating the thermochemical effect of Kondo screening of a local atomic spin by free electrons in the metal support. Inspired by the exothermicity of the spin-screening interaction, a novel approach to heterogeneous catalysis -- reaction on a rink (ROAR) -- is proposed. In contrast to the conventional notion of thermal catalytic reaction, lowering the temperature of metal support is predicted to result in a reduced reaction barrier. As a proof of concept, CO oxidation catalyzed by the Co@CoPc/Au(111) composite is scrutinized. By combining the density functional theory and a hierarchical equations of motion approach, it predicts that the existing s-d hybridization between the magnetic d orbital of Co adatom and the substrate metallic states in the transition state will lower the free energy barrier and accelerate the reaction rate. Furthermore, if the strength of s-d hybridization is enlarged, a more appreciable speedup will be achieved. This work highlights the potential usefulness of the spin degrees of freedom to heterogeneous single-atom catalysis, and our proposed ROAR approach could open up a new horizon for exploiting the role of atomic spin in chemical reactions.

scholarly journals Reaction on a Rink: Kondo-Enhanced Heterogeneous Single-Atom Catalysis

2021 ◽  
Author(s):  
Xiangyang Li ◽  
Hong Gong ◽  
Qingfeng Zhuang ◽  
Bing Wang ◽  
Xiao Zheng ◽  
...  
Keyword(s):  
Density Functional ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Single Atom ◽  
Spin Interaction ◽  
Free Energy Barrier ◽  
Free Electrons ◽  
Atomic Spin ◽  
Novel Approach ◽  
Metal Support

<p></p><p>Boosting the efficiency of heterogeneous single-atom catalysts (SACs) by adjusting the microenvironment of the active atom has recently attracted enormous attention. However, attempts to tune the spin-spin interaction between the SAC and its microenvironment have remained rather scarce. Some interesting questions can be raised, among which a fundamental one is: can the surrounding environment influence the local spin state of an SAC, and if so, can such influence be utilized to enhance the catalytic activity?</p> <p> </p> <p>In this work, we explore such a possibility by investigating the thermochemical effect of Kondo screening of a local atomic spin by free electrons in the metal support. Inspired by the exothermicity of the spin-screening interaction, a novel approach to heterogeneous catalysis -- reaction on a rink (ROAR) -- is proposed. In contrast to the conventional notion of thermal catalytic reaction, lowering the temperature of metal support is predicted to result in a reduced reaction barrier. As a proof of concept, CO oxidation catalyzed by the Co@CoPc/Au(111) composite is scrutinized. By combining the density functional theory and a hierarchical equations of motion approach, it predicts that the existing <i>s-d</i> hybridization between the magnetic <i>d</i> orbital of Co adatom and the substrate metallic states in the transition state will lower the free energy barrier and accelerate the reaction rate. Furthermore, if the strength of <i>s-d</i> hybridization is enlarged, a more appreciable speedup will be achieved.</p> <p> </p> <p>This work highlights the potential usefulness of the spin degrees of freedom to heterogeneous single-atom catalysis, and our proposed ROAR approach could open up a new horizon for exploiting the role of atomic spin in chemical reactions.</p><br><p></p>

scholarly journals Reaction on a Rink: Kondo-Enhanced Heterogeneous Single-Atom Catalysis

2021 ◽  
Author(s):  
Xiangyang Li ◽  
Hong Gong ◽  
Qingfeng Zhuang ◽  
Bing Wang ◽  
Xiao Zheng ◽  
...  
Keyword(s):  
Density Functional ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Single Atom ◽  
Spin Interaction ◽  
Free Energy Barrier ◽  
Free Electrons ◽  
Atomic Spin ◽  
Novel Approach ◽  
Metal Support

<p></p><p>Boosting the efficiency of heterogeneous single-atom catalysts (SACs) by adjusting the microenvironment of the active atom has recently attracted enormous attention. However, attempts to tune the spin-spin interaction between the SAC and its microenvironment have remained rather scarce. Some interesting questions can be raised, among which a fundamental one is: can the surrounding environment influence the local spin state of an SAC, and if so, can such influence be utilized to enhance the catalytic activity?</p> <p> </p> <p>In this work, we explore such a possibility by investigating the thermochemical effect of Kondo screening of a local atomic spin by free electrons in the metal support. Inspired by the exothermicity of the spin-screening interaction, a novel approach to heterogeneous catalysis -- reaction on a rink (ROAR) -- is proposed. In contrast to the conventional notion of thermal catalytic reaction, lowering the temperature of metal support is predicted to result in a reduced reaction barrier. As a proof of concept, CO oxidation catalyzed by the Co@CoPc/Au(111) composite is scrutinized. By combining the density functional theory and a hierarchical equations of motion approach, it predicts that the existing <i>s-d</i> hybridization between the magnetic <i>d</i> orbital of Co adatom and the substrate metallic states in the transition state will lower the free energy barrier and accelerate the reaction rate. Furthermore, if the strength of <i>s-d</i> hybridization is enlarged, a more appreciable speedup will be achieved.</p> <p> </p> <p>This work highlights the potential usefulness of the spin degrees of freedom to heterogeneous single-atom catalysis, and our proposed ROAR approach could open up a new horizon for exploiting the role of atomic spin in chemical reactions.</p><br><p></p>

scholarly journals Stability of heterogeneous single-atom catalysts: a scaling law mapping thermodynamics to kinetics

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Ya-Qiong Su ◽  
Long Zhang ◽  
Yifan Wang ◽  
Jin-Xun Liu ◽  
Valery Muravev ◽  
...  
Keyword(s):  
Metal Atom ◽  
Density Functional ◽  
Activation Barrier ◽  
Scaling Law ◽  
Precious Metals ◽  
Catalytic Performance ◽  
Single Atom ◽  
Atom Diffusion ◽  
Computational Screening ◽  
Metal Support

Abstract Heterogeneous single-atom catalysts (SACs) hold the promise of combining high catalytic performance with maximum utilization of often precious metals. We extend the current thermodynamic view of SAC stability in terms of the binding energy (Ebind) of single-metal atoms on a support to a kinetic (transport) one by considering the activation barrier for metal atom diffusion. A rapid computational screening approach allows predicting diffusion barriers for metal–support pairs based on Ebind of a metal atom to the support and the cohesive energy of the bulk metal (Ec). Metal–support combinations relevant to contemporary catalysis are explored by density functional theory. Assisted by machine-learning methods, we find that the diffusion activation barrier correlates with (Ebind)2/Ec in the physical descriptor space. This diffusion scaling-law provides a simple model for screening thermodynamics to kinetics of metal adatom on a support.

scholarly journals Single-atom alloy catalysts designed by first-principles calculations and artificial intelligence

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Zhong-Kang Han ◽  
Debalaya Sarker ◽  
Runhai Ouyang ◽  
Aliaksei Mazheika ◽  
Yi Gao ◽  
...  
Keyword(s):  
Data Analytics ◽  
Density Functional ◽  
Simultaneous Optimization ◽  
Single Atom ◽  
Subgroup Discovery ◽  
First Principles Calculations ◽  
Reliable Prediction ◽  
Novel Approach ◽  
Alloy Catalysts ◽  
Single Atom Alloy

AbstractSingle-atom-alloy catalysts (SAACs) have recently become a frontier in catalysis research. Simultaneous optimization of reactants’ facile dissociation and a balanced strength of intermediates’ binding make them highly efficient catalysts for several industrially important reactions. However, discovery of new SAACs is hindered by lack of fast yet reliable prediction of catalytic properties of the large number of candidates. We address this problem by applying a compressed-sensing data-analytics approach parameterized with density-functional inputs. Besides consistently predicting efficiency of the experimentally studied SAACs, we identify more than 200 yet unreported promising candidates. Some of these candidates are more stable and efficient than the reported ones. We have also introduced a novel approach to a qualitative analysis of complex symbolic regression models based on the data-mining method subgroup discovery. Our study demonstrates the importance of data analytics for avoiding bias in catalysis design, and provides a recipe for finding best SAACs for various applications.

scholarly journals A Novel, Oriented to Graphs Model of Robot Arm Dynamics

Robotics ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 128
Author(s):  
George Boiadjiev ◽  
Evgeniy Krastev ◽  
Ivan Chavdarov ◽  
Lyubomira Miteva
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Computer Experiments ◽  
Kinematic Chain ◽  
Robot Arm ◽  
Conservation Of Energy ◽  
Interdisciplinary Field ◽  
Novel Approach ◽  
Robot Arm Control

Robotics is an interdisciplinary field and there exist several well-known approaches to represent the dynamics model of a robot arm. The robot arm is an open kinematic chain of links connected through rotational and translational joints. In the general case, it is very difficult to obtain explicit expressions for the forces and the torques in the equations where the driving torques of the actuators produce desired motion of the gripper. The robot arm control depends significantly on the accuracy of the dynamic model. In the existing literature, the complexity of the dynamic model is reduced by linearization techniques or techniques like machine learning for the identification of unmodelled dynamics. This paper proposes a novel approach for deriving the equations of motion and the actuator torques of a robot arm with an arbitrary number of joints. The proposed approach for obtaining the dynamic model in closed form employs graph theory and the orthogonality principle, a powerful concept that serves as a generalization for the law of conservation of energy. The application of this approach is demonstrated using a 3D-printed planar robot arm with three degrees of freedom. Computer experiments for this robot are executed to validate the dynamic characteristics of the mathematical model of motion obtained by the application of the proposed approach. The results from the experiments are visualized and discussed in detail.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

2020 ◽  
Vol 1 (1) ◽  
pp. 93-102
Author(s):  
Carsten Strzalka ◽  
◽  
Manfred Zehn ◽  
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
A Priori ◽  
High Stress ◽  
Von Mises Stress ◽  
Detailed Knowledge ◽  
Variable Loading ◽  
Numerical Effort ◽  
Von Mises

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

DFT study on the hydrolysis of metsulfuron-methyl: A sulfonylurea herbicide

2018 ◽  
Vol 17 (08) ◽  
pp. 1850050 ◽  
Author(s):  
Qiuhan Luo ◽  
Gang Li ◽  
Junping Xiao ◽  
Chunhui Yin ◽  
Yahui He ◽  
...  
Keyword(s):  
Free Energy ◽  
Water Molecule ◽  
Carbonyl Group ◽  
Energy Barrier ◽  
Density Functional ◽  
Free Energy Barrier ◽  
Functional Theory ◽  
Metsulfuron Methyl ◽  
Catalytic Role ◽  
Hydrolysis Of

Sulfonylureas are an important group of herbicides widely used for a range of weeds and grasses control particularly in cereals. However, some of them tend to persist for years in environments. Hydrolysis is the primary pathway for their degradation. To understand the hydrolysis behavior of sulfonylurea herbicides, the hydrolysis mechanism of metsulfuron-methyl, a typical sulfonylurea, was investigated using density functional theory (DFT) at the B3LYP/6-31[Formula: see text]G(d,p) level. The hydrolysis of metsulfuron-methyl resembles nucleophilic substitution by a water molecule attacking the carbonyl group from aryl side (pathway a) or from heterocycle side (pathway b). In the direct hydrolysis, the carbonyl group is directly attacked by one water molecule to form benzene sulfonamide or heterocyclic amine; the free energy barrier is about 52–58[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. In the autocatalytic hydrolysis, with the second water molecule acting as a catalyst, the free energy barrier, which is about 43–45[Formula: see text]kcal[Formula: see text]mol[Formula: see text], is remarkably reduced by about 11[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is obvious that water molecules play a significant catalytic role during the hydrolysis of sulfonylureas.

scholarly journals Shaping quantum photonic states using free electrons

2021 ◽  
Vol 7 (11) ◽  
pp. eabe4270 ◽  
Author(s):  
A. Ben Hayun ◽  
O. Reinhardt ◽  
J. Nemirovsky ◽  
A. Karnieli ◽  
N. Rivera ◽  
...  
Keyword(s):  
Free Electron ◽  
Degrees Of Freedom ◽  
Free Electrons ◽  
Complete Control ◽  
Fock State ◽  
Judicious Choice ◽  
Electron Microscopes ◽  
Photonic States ◽  
Photonic Cavities ◽  
Electron Interactions

It is a long-standing goal to create light with unique quantum properties such as squeezing and entanglement. We propose the generation of quantum light using free-electron interactions, going beyond their already ubiquitous use in generating classical light. This concept is motivated by developments in electron microscopy, which recently demonstrated quantum free-electron interactions with light in photonic cavities. Such electron microscopes provide platforms for shaping quantum states of light through a judicious choice of the input light and electron states. Specifically, we show how electron energy combs implement photon displacement operations, creating displaced-Fock and displaced-squeezed states. We develop the theory for consecutive electron-cavity interactions with a common cavity and show how to generate any target Fock state. Looking forward, exploiting the degrees of freedom of electrons, light, and their interaction may achieve complete control over the quantum state of the generated light, leading to novel light statistics and correlations.

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