K_6CrNb_(15)O_(42)crystallizes in the hexagonal system with a=9.126(3)A,c=12.068(3)A,V= 870.4(5)A^3,and space group P6_2/mcm,Z=1.The structure was solved using direct method and Fourier Techniques.Of the 829 unique re...K_6CrNb_(15)O_(42)crystallizes in the hexagonal system with a=9.126(3)A,c=12.068(3)A,V= 870.4(5)A^3,and space group P6_2/mcm,Z=1.The structure was solved using direct method and Fourier Techniques.Of the 829 unique reflections measured by counter techniques,448 with I≥3σ(I) were used in the least-squares refinement of the model to R=0.034(R_w=0.044).The structure of KoCrNb_(15)O_(42)may be described as consisting of corner-shared and edge-shared octahedra,the ring units composed of six octahedra of Nb(1)are corner-shared one another along the c-axis to form hexagonal column octahedra chains which are connected by K^+ and octahedra of Nb(2).展开更多
The geometries,stabilities and electronic properties of Crn and CrnB(n=2-9) clusters have been systematically investigated by density functional theory.The results suggest that the lowest energy structures for CrnB cl...The geometries,stabilities and electronic properties of Crn and CrnB(n=2-9) clusters have been systematically investigated by density functional theory.The results suggest that the lowest energy structures for CrnB clusters can be obtained by substituting one Cr atom in Crn+1 clusters with B atom.The geometries of CrnB clusters are similar to that of Crn+1 clusters except for local structural distortion.The second-order difference and fragmentation energy show Cr4,Cr6,Cr8,Cr3B,Cr5B and Cr8B cluster are the most stable among these studied clusters.The impurity B increases the stabilities of chromium cluster.When B is doped on the Crn clusters,cluster geometry does dominate positive role in enhancing their stability.The doped B atom does not change the coupling way of the Cr site in Crn clusters,but breaks the symmetry and the Cr atoms are no longer equivalent.The doped B atom increases the total magnetic moments of Crn in most cases.展开更多
文摘K_6CrNb_(15)O_(42)crystallizes in the hexagonal system with a=9.126(3)A,c=12.068(3)A,V= 870.4(5)A^3,and space group P6_2/mcm,Z=1.The structure was solved using direct method and Fourier Techniques.Of the 829 unique reflections measured by counter techniques,448 with I≥3σ(I) were used in the least-squares refinement of the model to R=0.034(R_w=0.044).The structure of KoCrNb_(15)O_(42)may be described as consisting of corner-shared and edge-shared octahedra,the ring units composed of six octahedra of Nb(1)are corner-shared one another along the c-axis to form hexagonal column octahedra chains which are connected by K^+ and octahedra of Nb(2).
基金supported by the Foundation Start Up for High Level Talents of Shihezi University, China (Grant No. RCZX200747)
文摘The geometries,stabilities and electronic properties of Crn and CrnB(n=2-9) clusters have been systematically investigated by density functional theory.The results suggest that the lowest energy structures for CrnB clusters can be obtained by substituting one Cr atom in Crn+1 clusters with B atom.The geometries of CrnB clusters are similar to that of Crn+1 clusters except for local structural distortion.The second-order difference and fragmentation energy show Cr4,Cr6,Cr8,Cr3B,Cr5B and Cr8B cluster are the most stable among these studied clusters.The impurity B increases the stabilities of chromium cluster.When B is doped on the Crn clusters,cluster geometry does dominate positive role in enhancing their stability.The doped B atom does not change the coupling way of the Cr site in Crn clusters,but breaks the symmetry and the Cr atoms are no longer equivalent.The doped B atom increases the total magnetic moments of Crn in most cases.
