A First-principles Study On Structural Regulation Of The Catalytic Growth Of Single-walled Carbon Nanotubes By Co-based Mixed Metal Clusters

The single-walled carbon nanotubes(SWCNT)have excellent electrical properties,and exhibit great potential applications in many fields.The Chemical Vapor Deposition method which can produce SWCNT with high quality in large quantities has become the main method to prepare SWCNT.However,until now,SWCNT with single chirality can still not be prepared in experiment,because the growth process of SWCNT can be affected by many factors,such as pressure,carbon source,temperature,catalyst,etc..And the catalyst is the most critical factor for preparation of SWCNT.Based on density functional theory,the following two topics are studied:? Density-functional investigations on the magnetic properties of the mixed Fe,Coand Ni clustersBased on the 13-atom icosahedral structural model,the magnetic properties of Fe,Coand Ni single and binary mixed clusters are systematically investigated with thedensity-functional calculations.It is found that the sensitivity of cluster magnetism on structural distortion decreases with the order of Fe,Coand Ni at finite temperature,and that the icosahedral Fe₁₃and Co₁₃all have near-degenerate low energy states with different magnetic moments.There is no abnormal phenomenon for the change of the magnetic moment of the mixed clusters of FeNi and CoNi with the composition,but there are few abnormal phenomena for the evolution of the magnetic moment of the mixed clusters of FeCowith the composition.We believe that this abnormal phenomenon can provide a possible theoretical explanation for the experimental observations in FeCoamorphous alloy.? First-Principles study of structural control of Comixed metal clusters catalytic growth single wall carbon nanotubesBased on the 55-atom structural model with the icosahedral(I_h)symmetry,the mixed metal catalysts Co₅₄M_1tand Co₅₄M_1cwhich can be constructed through replacing one Coatom on the surface site(t,top)or in the center site(c,center)of the Co₅₅cluster by a single atom M(M=Mo,Pt,Ru,W,Cu)were studied.Then the armchair(5,5)-SWCNT and zigzag(10,0)-SWCNT were adsorbed on the surface of Co₅₅and Co₅₄M_1t/cat the top and the bridge position,respectively.Comparing with Co₅₅,it was found that,Co₅₄M_1t/call have obvious structural regulation for(5,5)-SWCNT;however,Co₅₄M_1t/chave nearly no structural regulation for(10,0)-SWCNT.Through comparing the interaction between different SWCNT and different catalysts,it can be concluded that,for(5,5)-SWCNT the absorption of Co₅₄Pt_1twas the strongest;And for(10,0)-SWCNT the absorption of Co₅₄W_1twas the strongest.And the absorbed properties of those two catalysts were all superior to that of Co₅₅.This work has some enlightenment on the synthesis of different chiral SWCNT.