A Density Functional Theory Study For Ni Alloy Clusters

In this paper, Gaussian03 program based on density functional theory is applied. The geometric structures of Mg/Ni , W/Ni and Pt/Ni alloy clusters are all optimized systematically, and the the ground state structures or the stable structures are investigated. The main results are as follows:Firstly, possible geometrical structures of Mg_xNi(yx+y≤5)clusters have been optimized by using the hybrid density functional theory(B3LYP) at the 6-311+G level. For the ground state structures of Mg_xNi_y(x+y≤5) clusters, the average binding energy, energy gap and natural bonding orbits(NBO) of Mg_xNi_y(x+y≤5) clusters are studied. We find that the ground state structures and symmetries of the clusters with the adulteration of Mg and Ni atoms vary obviously compared to the pure clusters, and the clusters become more stable with increasing the bonds of Ni atom formed. Most of Mg atom are positive, while Ni atom is negative in the alloy clusters. Moreover, it is very easy to form new alloy material with other systems as the very strong ability of Ni atom on charge regulation.Secondly, possible geometrical structures of Mg_xNi_y(x=1, 2; y=1⁵) clusters have been optimized by using the hybrid density functional theory(B3LYP) at the 6-311+G level, the thermodynamic, nucleus independent chemical shifts(NICS), vibration spectrum, magnetism and polarizability of the ground state structures are studied. The results show: the stable structures of the MgNiy and Mg₂Ni_y clusters can be obtained by adding one Ni atom to MgNiy-1 and Mg₂Ni_y-1 clusters relatively. The magnetic moment shows odd-even oscillation with increasing Ni atom in MgNiy(y=1⁵) clusters.Third, possible geometrical structures of W_nNi_m(n+m≤7) clusters have been studied by using density functional theory at the B3PW91/LANL2DZ level. For the ground state structures, the average binding energy, energy gap, thermodynamic, NICS, frequency, spectrum, NBO, magnetism and polarizability are studied. The results show: the structures of W_nNi_m clusters are more stable with increasing W content, the rich W clusters are more stable than the Ni-rich, W-W bond plays a great role on the stability of W_nNi_m clusters. Multiple aromaticity is found in WNi₅, W₂Ni₄, W₄Ni₂, W2Ni₅ and W4Ni3 clusters, and W5Ni cluster show non-aromaticity. The hybrid phenomenon is very strong within W and Ni atoms, while weak in the W-Ni atoms. It is very easy to form new alloy material with other systems as the very strong ability of W atom on charge regulation. The magnetic moment on the W-atom of W2Nim(m≤5) clusters, its odd-numbered clusters are larger than the corresponding even-numbered clusters. At last, all the possible geometrical structures of Pt_nNi_m(n+m=6, n,m≠0) clusters are optimized with a hybrid Density functional theory(B3LYP) at LANL2DZ level. For the ground state structures, the thermodynamic, NICS, vibration spectrum, NBO, magnetism and polarizability of the ground state structures are studied. The results show: the ground state structures of PtNi₅, Pt₂Ni₄ and Pt₃Ni₃ clusters are quadrangular bi-pyramid, Pt₄Ni₂ and Pt₅Ni clusters are triangular bi-pyramid with hat and triangular pyramid with quadrilateral, respectively. Aromaticity is found in Pt₂Ni₄ and Pt₅Ni clusters, while antiaromaticity is found in PtNi₅ cluster. The hybrid phenomenon are very strong within and between Pt and Ni atom, and it is quite easy to form new alloy material with other systems as the very strong ability of Pt atom on charge regulation. PtNi₅, Pt₂Ni₄ and Pt₄Ni₂ clusters appear ferromagnetism, and the anti-ferromagnetic on Pt₃Ni₃ and Pt₅Ni clusters. The IR and raman absorption peak of PtNi₅ , IR of Pt₂Ni₄, Raman of Pt₃Ni₃ and Pt₄Ni₂ have only one. The absorption peak of Pt₅Ni appears in the bigger frequencies only, and is zero almost in the small frequencies.Above all, it is the first time to study the physical and chemical properties of the ground state of Mg_xNi_y(x+y≤5), Mg_xNi_y(x=1, 2; y=1⁵), W_nNi_m(n+m≤7) and Pt_nNi_m(n+m=6, n,m≠0) clusters. All of these cluster researches will play an important role in finding new functional materials.