Theoretical Study On Structure And Properties Of Transition Metal Co Doped Germanium Clusters CoGe_n(n=2-12)

Clusters can be utilized not only as the basic unit for assembling materials,but also as designing novel materials depending on changing the size and shape of atomic clusters.Germanium is widely used in nanomaterials,magnetic storage,environmental catalytic materials and other fields due to its high hole mobility among all semiconductors.The study found that transition metal-doped pure germanium clusters can possess the unique thermodynamic stability and the chemical stability of the clusters.In this paper,following using ABCluster global search technology searching the initial configuration of anion and neutral cobalt-doped germanium clusters Co Ge_n^-/0（n=2-12）,the Coupled Cluster method（CCSD（T））is used to systematically study their the ground state structures and related physical and chemical properties,as well as the m PW2PLYP double-hybrid density functional method used for the ground state structures and physical and chemical properties of cationic cobalt-doped germanium clusters Co Ge_n⁺（n=2-12）.CCSD（T）method combined with cc-pVTZ-DK basis set was used for studing the ground state structures and properties of Co Ge_n^-/0（n=2-12）clusters.The results are shown that:（1）the growth pattern of the most stable anionic Co Ge_n^-（n=2-12）clusters is exhibited as follows:when n≤8,the cobalt atom replaces a Ge atom in the ground state structures of Ge^-_n+1cluster;when n=9,the semi-cage structure is formed;when n≥10,the cobalt atom is embedded into the center of the germanium cage structures;（2）the growth pattern of the most stable neutral Co Ge_n（n=2-12）clusters is exhibited as follows:when n≤7,the Co atom replaces a Ge atom in Ge_n+1cluster（except Co Ge₃）;when n=9,the semi-cage structure is formed;when n≥10,cage structures is formed;（3）from the stability analysis,the anionic clusters are more stable than their corresponding neutral clusters,indicating that the stability of the clusters can be improved by acquiring an electron;（4）the adiabatic electron affinity（AEA）of Co Ge_n^-（n=2-12）clusters were predicted,calculated vertical electron dissociation energy（VDE）and the simulated photoelectron spectra（PES）of anion Co Ge_n^-（n=2-12）clusters were predicted using P3 method.Furthermore,the theoretical PES is also in good agreement with the experimental PES,which indicates that the ground state structure of anion is reliable.In addition,HOMO-LUMO gap,natural population analysis（NPA）and magnetic moment of Co Ge_n^-/0（n=2-12）system are calculated by m PW2PLYP/aug-cc-pVTZ//m PW2PLYP/cc-pVTZ method.The results are shown that:（1）from HOMO-LUMO gap,Co Ge₁₀^-has a higher E_gapafter cluster form cage,Co Ge₁₀^-has a higher chemical stability;（2）the natural population analysis indicates that the orbitals of cobalt atom in anionic and neutral clusters have strong spd hybridization;（3）the result of magnetic moment calculation indicates that the magnetic moment of clusters is mainly provided by cobalt atoms before they forming cage structure.Double-hybrid density functional mPW2PLYP method combined with the aug-cc-pVTZ basis set was used for studing the ground state configurations and properties of cationic clusters Co Ge_n⁺（n=2-12）.The results show that:（1）the growth mode of the most stable cationic Co Ge_n⁺（n=2-12）clusters is exhibited as follows:when n≤7（except Co Ge₄⁺）,it is the replacement structure of a cobalt atom replaced on the ground state structure of Ge⁺_n+1clusters;when n=9,the semi-cage configuration is formed;when n≥10,the cage structure is formed;（2）from the stability analysis,the average bond energy of cationic and anionic clusters are higher than those of their corresponding neutral clusters,indicating that gaining or losing an electron both can enhance the stability of CoGe_n（n=2-12）clusters.