The Crystal Structure And Edd Of The Co-v-r Compounds

The crystal structure of the Co₄₀V_60-2xLa_x compound and Co₃₅V₆₀Nd_2.5 compound have been systematically investigated by the X-ray diffraction. On the basis of crystal structure refinement, we calculated the (Fo-Fc) difference and get the pattern of the difference fourier synthesis. According to the analysis of difference fourier synthesis, we construct the three structural models and analyze the occupation of the rare-earth La in Co-Vσphase. Furthermore, the powder data of Co4 0 V6 0-2xL a x and Co₃₅V₆₀Nd_2.5 were calculated by maximum-entropy-method with the program of Prima.and acquired the patterns of three dimensional electron density distributions.The Co V La compounds had been prepared by arc metling. The X-ray diffraction reveals that all the Co₄₀V_60-2xLa_x compounds crystallize in single phase. The substitution of La for V leads to decreases of the lattice parameters and the lattice parameters of Co₄₀V_60-2xLa_x is larger than the corresponding Co-V binary system. The patterns of difference fourier synthesis were acquired by calculating the structure refinement data of Co-V binary system. From the section of Z=0.5 and Z=1, we can observe the electron density distributions in the 4f and 4g position. We can construct the structural models base on them. We comfirm the occupations of the rare-earth La in Co-Vσphase after refining the three structural models. Compare with the 4f and 4g structural models, the observed data and calculated data are very close in vacancy model and the ingredient of La which calculated by occupancy is close with the experimental ingredient. The results are more reasonable than 4f and 4g models. The vacancy models give us clear distributions of rare-earth La in Co-Vσphase. Finally, we calculate the three dimensional electron density distributions of Co₄₀V_60-2xLa_xcompounds by maximum-entropy-method. The electron density of 4f and 4g positions show that there are some electrons of atoms overlapped. According to this phenomenon, we can infer that the interaction of some atoms is combined with covalent bond. 40 60-2x xThe Co₃₅V₆₀Nd_2.5 compound had been synthesized by sucking cast into a Cu mold. The X-ray diffraction reveals that the Co₃₅V₆₀Nd_2.5 compound is crystallized inσphase. The patterns of difference fourier synthesis were acquired by calculating the structure refinement data of Co-V binary system and the structural models of 4f, 4g and vacancy are constructed. We comfirm the occupations of the rare-earth Nd in Co-Vσphase after refining the three structural models. Finally, we calculate the three dimensional electron density distributions of Co₃₅V₆₀Nd_2.5 compounds by maximum-entropy-method. According to electron density distributions, we can infer that the interaction of some atoms is combined with covalent bond.