(MN)nHm(M=Ga,In; n=1-4; m=1, 2)团簇的结构与稳定性

采用密度泛函理论(DFT)的B3LYP方法, 在6-31G**和Lanl2dz水平上分别对(MN)nHm(M=Ga, In; n=1-4; m=1, 2)进行了优化和振动频率计算. 得到了上述团簇的最稳定构型、H原子的结合能以及它们的能隙. 结果表明, (MN)nH(M=Ga, In; n=1-4)的基态构型均为双重态, (MN)nH2(M=Ga, In; n=1-4)的基态构型均为单重态; 当氢的个数为1时, 加在N原子上比加在M(M=Ga, In)原子上稳定, 如有N3单元, 那么加在N3单元两侧的构型是相同的, 且它是最稳定的; 当氢的个数为2时, 除n=1外, 分别加在两个N原子上的构型是最稳定的, 如有N3单元, 那么分别加在N3单元分离最远的两个N原子的构型是最稳定的. GaNH、(GaN)3H 和InNH的结合能和能隙都很大, 说明这些团簇都有很高的稳定性.

Structure and Stability of (MN)nHm(M=Ga, In; n=1-4; m=1, 2) Clusters

Using density functional theory associated with B3LYP method with 6-31G** and Lanl2dz basis sets, the optimization of the geometries and the calculation of frequencies for (MN)nHm (M=Ga, In; n= 1-4; m=1, 2) clusters were carried out, respectively. In addition, the most stable structures, binding energy of hydrogen atom, and energy gap were obtained. The results showed that the ground state structures of (MN)nH (M=Ga, In; n=1-4) and (MN)nH2(M=Ga, In; n=1-4) clusters were doublet and singlet states, respectively. When the number of hydrogen atom was one, the isomer in which hydrogen atomwas added in nitrogen atomwas more stable than that in M(M=Ga, In) atom. If there was a N3 unit, the isomers in which hydrogen atom was added in nitrogen atom of either side in N3 unit were the same and the most stable. While the number of hydrogen atom was two, except for n is equal to one, the isomer in which two hydrogen atoms were added in nitrogen atoms, respectively, was the most stable. If there was a N3 unit, the isomer in which two hydrogen atoms were added in the two farthest nitrogen atoms in N3 unit, respectively, was the most stable. Larger binding energies of a single hydrogen atom on small MN clusters and larger highest occupied and lowest unoccupied molecular-orbital energy gaps for GaNH, (GaN)3H, and InNH make these species have more stable.