An approximate calculation of the exchange interaction constant J_(RT)between the rare-earth sublattice and the transition metal sublattice in R_2Fe_(17-x)Al_x (R= Tb,Gd, and Dy) compounds is given by the molecular-fi...An approximate calculation of the exchange interaction constant J_(RT)between the rare-earth sublattice and the transition metal sublattice in R_2Fe_(17-x)Al_x (R= Tb,Gd, and Dy) compounds is given by the molecular-field model and the results of neutron diffraction.The calculated values, -J_(R,T)/k, for Dy_2Fe_(17-x)Al_x (x=5, 6, 7 and 8), Tb_2Fe_(10)Al_7,Gd_2Fe_(17-x)Al_x (x=7, 8) compounds are 8.62K, 8.64K, 9.52K, 10.34K and 10.66K, 10.65K, and 9.85K,respectively, they are in agreement with the experimental values, -J_(R,T)/k, of Dy_2Fe_(17-x)Al_x(x=5, 6, 7 and 8), Tb_2Fe_(10)Al_7 and Gd_2Fe_(17-x)Al_x (x=7, 8) compounds, which are 8.77K, 9.25K,10.1K, 10.9K and 10.35K, 10.1K, and 10.3K, respectively. The origins of the difference between thecalculated and the experimental results are discussed.展开更多
Density functional theory at the BP86 level was used to investigate the influence of equatorial ligands on the Ni–Ni interactions and magnetic coupling properties of metal string complexes [Ni3（L）4（NCS）2] （L rep...Density functional theory at the BP86 level was used to investigate the influence of equatorial ligands on the Ni–Ni interactions and magnetic coupling properties of metal string complexes [Ni3（L）4（NCS）2] （L represents the rigid equatorial ligands; L = dzp- （1）, mpmpa- （2）, mppda- （3）, mptpa- （4））. The following conclusions can be drawn. （1） With increasing the radius of the connecting atom in the cental ring in equatorial ligands, the two pyridine rings bend down, resulting in the decreasing distance between the two pyridine-nitrogen atoms and the Ni–Ni distance. Therefore, the strength order of the Ni–Ni interaction is 4 〉 2 〉 3 〉 1. The Ni–Ni interactions in 2 and 4 are stronger than those in Ni3（dpa）4（NCS）2 containing no-rigid equatorial ligands. （2） The calculated -Jab is 4 〉 2 〉 3 〉 1. There are two types of magnetic exchange pathways in these complexes： the σ-type pathway through the Ni36＋ chains and the δ-type pathway through the equatorial ligands. The magnetic coupling through the metals is the dominant part. Hence, the magnetic coupling strength increases with increasing the Ni–Ni interaction. Modifying the radius of the connecting atom may be one of the means to fine tuning of magnetic coupling strength of this kind of metal string complexes.展开更多
Davidson and Clark’s equations for calculating the local spin of molecules were rewritten and simplified as matrices algebra. By applying our program, we calculated the local spin of O2 and NO molecules and obtained ...Davidson and Clark’s equations for calculating the local spin of molecules were rewritten and simplified as matrices algebra. By applying our program, we calculated the local spin of O2 and NO molecules and obtained almost the same results as those by Davidson and Clark’s method. The local spin and the magnetic coupling constant J of the simple Van der Waals complex HHeH were calculated as well to investigate the relationship between the geometric structures and magnetic values.展开更多
基金This work was supported by the Research Fund of Hebei Education Committee(Grant No.2001108).
文摘An approximate calculation of the exchange interaction constant J_(RT)between the rare-earth sublattice and the transition metal sublattice in R_2Fe_(17-x)Al_x (R= Tb,Gd, and Dy) compounds is given by the molecular-field model and the results of neutron diffraction.The calculated values, -J_(R,T)/k, for Dy_2Fe_(17-x)Al_x (x=5, 6, 7 and 8), Tb_2Fe_(10)Al_7,Gd_2Fe_(17-x)Al_x (x=7, 8) compounds are 8.62K, 8.64K, 9.52K, 10.34K and 10.66K, 10.65K, and 9.85K,respectively, they are in agreement with the experimental values, -J_(R,T)/k, of Dy_2Fe_(17-x)Al_x(x=5, 6, 7 and 8), Tb_2Fe_(10)Al_7 and Gd_2Fe_(17-x)Al_x (x=7, 8) compounds, which are 8.77K, 9.25K,10.1K, 10.9K and 10.35K, 10.1K, and 10.3K, respectively. The origins of the difference between thecalculated and the experimental results are discussed.
基金supported by the Natural Science Foundation of Guangdong Province(S2012010008763)Ministry of Education and Guangdong Province(2010B090400184)Science and Technology Program of Guangzhou City(2011J4300063)
文摘Density functional theory at the BP86 level was used to investigate the influence of equatorial ligands on the Ni–Ni interactions and magnetic coupling properties of metal string complexes [Ni3（L）4（NCS）2] （L represents the rigid equatorial ligands; L = dzp- （1）, mpmpa- （2）, mppda- （3）, mptpa- （4））. The following conclusions can be drawn. （1） With increasing the radius of the connecting atom in the cental ring in equatorial ligands, the two pyridine rings bend down, resulting in the decreasing distance between the two pyridine-nitrogen atoms and the Ni–Ni distance. Therefore, the strength order of the Ni–Ni interaction is 4 〉 2 〉 3 〉 1. The Ni–Ni interactions in 2 and 4 are stronger than those in Ni3（dpa）4（NCS）2 containing no-rigid equatorial ligands. （2） The calculated -Jab is 4 〉 2 〉 3 〉 1. There are two types of magnetic exchange pathways in these complexes： the σ-type pathway through the Ni36＋ chains and the δ-type pathway through the equatorial ligands. The magnetic coupling through the metals is the dominant part. Hence, the magnetic coupling strength increases with increasing the Ni–Ni interaction. Modifying the radius of the connecting atom may be one of the means to fine tuning of magnetic coupling strength of this kind of metal string complexes.
基金Major State Bas ic Research Development Program of Sic.and Tech.Mhinistry(Gant No.G 200077500)Major Project of Resesrch of NSFC(Grcnt No.90101028).
文摘Davidson and Clark’s equations for calculating the local spin of molecules were rewritten and simplified as matrices algebra. By applying our program, we calculated the local spin of O2 and NO molecules and obtained almost the same results as those by Davidson and Clark’s method. The local spin and the magnetic coupling constant J of the simple Van der Waals complex HHeH were calculated as well to investigate the relationship between the geometric structures and magnetic values.
