In this study,the thermal stabilities of trimetallic nanoclusters of AgPd@Pt with different morphologies of cuboctahedron(CO),icosahedron(Ih),decahedron(Dh),octahedron(Oh),and Marks-decahedron(m-Dh)have been investiga...In this study,the thermal stabilities of trimetallic nanoclusters of AgPd@Pt with different morphologies of cuboctahedron(CO),icosahedron(Ih),decahedron(Dh),octahedron(Oh),and Marks-decahedron(m-Dh)have been investigated using molecular dynamics(MD)simulation.Our results showed that the core@shell nanostructure is unstable in all morphologies before the melting point and the Ag and Pd atoms at the nanocluster core diffuse to the cluster shell to form a mixed pseudo-spherical structure,which is more stable and has lower energy.The MD results also showed that the melting points of AgPd@Pt nanoclusters are dependent on the nanocluster morphology and obey the following trend:m-Dh>Oh>Dh>CO>Ih.It is also shown that the surface effect is the most important effect on the thermal stability of these nanoclusters.展开更多
We have investigated the formation of pure Ir,Ir_(0.75)Au_(0.25),Ir_(0.5)Au_(0.5),Ir_(0.25)Au_(0.75),and pure Au nanoclusters through the inert-gas condensation method using MD simulation.The effects of mole fraction,...We have investigated the formation of pure Ir,Ir_(0.75)Au_(0.25),Ir_(0.5)Au_(0.5),Ir_(0.25)Au_(0.75),and pure Au nanoclusters through the inert-gas condensation method using MD simulation.The effects of mole fraction,temperature,and pressure on the different thermodynamic and structural properties of the produced nanoclusters have been investigated.The results showed that the size and number of the formed clusters increased with the increasing temperature and pressure;this was in good agreement with the experimental results obtained for metallic clusters.Our results also show that the stability of the produced nanoclusters increases as the Au mole fraction increases,whereas their stability decreases as the temperature and pressure increase.The Au atoms tend to lie on the cluster surface,whereas the Ir atoms tend to lie at the cluster cores.The percent of the surface Au atoms also increased as the Au mole fraction,temperature,and pressure increased.The radial distribution function(RDF)results indicate that the core–shell structures have not been produced in these simulations.We have also shown that the sphericity of the produced smaller clusters increases with the increasing Au mole fraction.The sphericity also increased with the increasing temperature and pressure.Our structural investigations also showed that some ordered clusters containing the fcc and hcp atoms were formed during these simulations.The percentage of the fcc atoms also increased with the increasing pressure.However,the surface of the produced clusters contained disordered atoms.展开更多
In this study,the thermal behaviors of pure Ni and Pd as well as Ni@Pd,and Pd@Ni hollow nanoclusters were investigated by MD simulations.The Ni@Pd hollow nanoclusters exhibited more thermodynamic stability and a highe...In this study,the thermal behaviors of pure Ni and Pd as well as Ni@Pd,and Pd@Ni hollow nanoclusters were investigated by MD simulations.The Ni@Pd hollow nanoclusters exhibited more thermodynamic stability and a higher melting point than the Pd@Ni ones.This result is opposite to the trend demonstrated by the corresponding bulk materials,which could be related to the effect of the hollow core.Due to the small difference between the melting points of bulk Pd and Ni,a two-step melting behavior was not observed for the hollow Pd–Ni nanoclusters.The differences between the thermodynamic stabilities of the simulated nanoclusters were related to the concentration of Pd atoms in the shell and Ni atoms in the core regions due to the lower surface energy of Pd atoms and the higher cohesive and binding energy of Ni atoms.Also,a larger nanocluster size led to a faster diffusion of Pd atoms toward the shell of the nanocluster.Moreover,the diffusion of Pd atoms to the surface and Ni atoms to the core region for Pd@Ni nanoclusters near the melting point and the increase in the ordered atoms under these circumstances led to a higher melting point of this nanocluster in comparison with the Ni@Pd nanoclusters.These results indicate the potential for the future construction of nanocatalysts based on bimetallic nanoclusters with core–shell hollow structures.展开更多
文摘In this study,the thermal stabilities of trimetallic nanoclusters of AgPd@Pt with different morphologies of cuboctahedron(CO),icosahedron(Ih),decahedron(Dh),octahedron(Oh),and Marks-decahedron(m-Dh)have been investigated using molecular dynamics(MD)simulation.Our results showed that the core@shell nanostructure is unstable in all morphologies before the melting point and the Ag and Pd atoms at the nanocluster core diffuse to the cluster shell to form a mixed pseudo-spherical structure,which is more stable and has lower energy.The MD results also showed that the melting points of AgPd@Pt nanoclusters are dependent on the nanocluster morphology and obey the following trend:m-Dh>Oh>Dh>CO>Ih.It is also shown that the surface effect is the most important effect on the thermal stability of these nanoclusters.
文摘We have investigated the formation of pure Ir,Ir_(0.75)Au_(0.25),Ir_(0.5)Au_(0.5),Ir_(0.25)Au_(0.75),and pure Au nanoclusters through the inert-gas condensation method using MD simulation.The effects of mole fraction,temperature,and pressure on the different thermodynamic and structural properties of the produced nanoclusters have been investigated.The results showed that the size and number of the formed clusters increased with the increasing temperature and pressure;this was in good agreement with the experimental results obtained for metallic clusters.Our results also show that the stability of the produced nanoclusters increases as the Au mole fraction increases,whereas their stability decreases as the temperature and pressure increase.The Au atoms tend to lie on the cluster surface,whereas the Ir atoms tend to lie at the cluster cores.The percent of the surface Au atoms also increased as the Au mole fraction,temperature,and pressure increased.The radial distribution function(RDF)results indicate that the core–shell structures have not been produced in these simulations.We have also shown that the sphericity of the produced smaller clusters increases with the increasing Au mole fraction.The sphericity also increased with the increasing temperature and pressure.Our structural investigations also showed that some ordered clusters containing the fcc and hcp atoms were formed during these simulations.The percentage of the fcc atoms also increased with the increasing pressure.However,the surface of the produced clusters contained disordered atoms.
文摘In this study,the thermal behaviors of pure Ni and Pd as well as Ni@Pd,and Pd@Ni hollow nanoclusters were investigated by MD simulations.The Ni@Pd hollow nanoclusters exhibited more thermodynamic stability and a higher melting point than the Pd@Ni ones.This result is opposite to the trend demonstrated by the corresponding bulk materials,which could be related to the effect of the hollow core.Due to the small difference between the melting points of bulk Pd and Ni,a two-step melting behavior was not observed for the hollow Pd–Ni nanoclusters.The differences between the thermodynamic stabilities of the simulated nanoclusters were related to the concentration of Pd atoms in the shell and Ni atoms in the core regions due to the lower surface energy of Pd atoms and the higher cohesive and binding energy of Ni atoms.Also,a larger nanocluster size led to a faster diffusion of Pd atoms toward the shell of the nanocluster.Moreover,the diffusion of Pd atoms to the surface and Ni atoms to the core region for Pd@Ni nanoclusters near the melting point and the increase in the ordered atoms under these circumstances led to a higher melting point of this nanocluster in comparison with the Ni@Pd nanoclusters.These results indicate the potential for the future construction of nanocatalysts based on bimetallic nanoclusters with core–shell hollow structures.
