Structural,electronic, and magnetic properties of 3d transition metal doped GaN nanosheet: A first‐principles study

We have performed the first‐principles calculations on the structural, electronic, and magnetic properties of 3d transition‐metal? (Cr, Mn, Fe, Co, and Ni) atoms doped 2D GaN nanosheet. The results show that 3d TM atom substituting one Ga leads to a structural reconstruction around the 3d TM impurity compared to the pristine GaN nanosheet. The doping of TM atom can induce magnetic moments, which are mainly located on the 3d TM atom and its nearest‐neighbor N atoms. It is found that Mn‐ and Ni‐doped GaN nanosheet with 100% spin polarization characters seem to be good candidates for spintronic applications. When two Ga atoms are substituted by two TM dopants, the ferromagnetic (FM) ordering becomes energetically more favorable for Cr‐, Mn‐, and Ni‐doped GaN nanosheet with different distances of two TM atoms. On the contrary, the antiferromagnetic (AFM) ordering is energetically more favorable for Fe‐doped GaN nanosheet. In addition, our GGA + U calculations show the similar results with GGA calculations. © 2016 Wiley Periodicals, Inc.     

Energy Stabilities,Magnetic Properties,and Electronic Structures of Diluted Magnetic Semiconductor Zn1-xMnxS(001) Thin Films

We investigate the electronic and magnetic properties of the diluted magnetic semiconductors Zn_1-xMn_xS(001) thin films with different Mn doping concentrations using the total energy density functional theory. The energy stability and density of states of a single Mn atom and two Mn atoms at various doped configurations and different magnetic coupling state were calculated. Different doping configurations have different degrees of p-d hybridization, and because Mn atoms are located in different crystal-field environment, the 3d projected densities of states peak splitting of different Mn doping configurations are quite different. In the two Mn atoms doped, the calculated ground states of three kinds of stable configurations are anti-ferromagnetic state. We analyzed the 3d density of states diagram of three kinds of energy stability configurations with the two Mn atoms in different magnetic coupling state. When the two Mn atoms are ferromagnetic coupling, due to d-d electron interactions, density of states of anti-bonding state have significant broadening peaks. As the concentration of Mn atoms increases, there is a tendency for Mn atoms to form nearest neighbors and cluster around S. For such these configurations, the antiferromagnetic coupling between Mn atoms is energetically more favorable.     

钙钛矿型复合稀土铁氧化物电子结构的第一性原理研究

采用基于赝势平面波基组的第一性原理方法对一系列具有钙钛矿结构的复合稀土铁氧化物RFeO₃ (R＝镧系稀土元素)的构型和电子结构进行了系统研究. 考察了铁磁(FM)和反铁磁(AFM)两种磁结构, 其中AFM型在常温下更为稳定, 且其构型优化结果更接近于实验测量值. 不论是FM还是AFM构型, R原子的磁距均与自由R^3＋离子相同; 对于Fe原子, 在FM结构中的磁距较AFM类型来得小; 随着R原子序数的增加, 两种磁结构中Fe原子的磁距均呈减小趋势; 对于相同类型的RFeO₃化合物, 具有非常类似的能带结构, 其中AFM构型在费米能级处存在明显的带隙, 而FM型化合物则具有金属特性.     

Structure and properties of Mn(n), Mn(n)-, and Mn(n)+ clusters (n = 3-10)

Electronic and geometrical structures of Mn(3)-Mn(10) together with their singly negatively and positively charged ions are computed using density functional theory with generalized gradient approximation. The ground-state spin multiplicities in the neutral series are 16, 21, 4, 9, 6, 5, 2, and 5, for Mn(3)-Mn(10), respectively. Thus, there is a transition from a ferromagnetic ground state to a ferrimagnetic ground state at Mn(5). The energy difference between ferrimagnetic and ferromagnetic states in Mn(n) grows rapidly with increasing n and exceeds 2 eV in Mn(10). The corresponding change from ferro- to ferrimagnetic ground state occurs at Mn(6)(-) and Mn(3)(+) in the anionic and cationic series, respectively. Beginning with Mn(6), the ion spin multiplicities differ from that of the neutral by +/-1 (i.e., they obey the empirical "+/-1 rule"). We found that the energy required to remove an Mn atom is nearly independent of the charge state of an Mn(n) cluster and the number of atoms in the cluster, except for Mn(3). The results of our calculations are in reasonable agreement with experiment, except for the experimental data on the magnetic moments per atom, where, in general, we predict smaller values than the experiment.     

Structural, electronic, and magnetic properties of manganese-doped Zn12O12 clusters: a first-principles study

A first-principles study has been performed to evaluate the structural, electronic, and magnetic properties of Zn(12)O(12) clusters doped with one or two Mn atoms. The substitutional, exohedral, and endohedral dopings are taken into account. For the monodoped clusters, the substitutional isomer is most energetically favorable, and an exohedral isomer may appear as a low-lying metastable state. All isomers present 5 mu(B) magnetic moment that is mainly contributed by the Mn-3d component. For the bidoped clusters, the antiferromagnetic state is degenerate with the ferromagnetic state at larger Mn-Mn distance (>5 A), while it is more energetically favorable at smaller Mn-Mn distance. Thus, the cohesion of bidoped isomer is sensitive to the magnetic coupling or chemical bonding. The endohedral bidoped isomer is found to be a stable local minimum, and the direct Mn-Mn interaction causes the reduction of local magnetic moment of Mn to about 4 mu(B).     

Low-energy isomer identification, structural evolution, and magnetic properties in manganese-doped gold clusters MnAu(n) (n = 1-16)

The size-dependent electronic, structural, and magnetic properties of Mn-doped gold clusters have been systematically investigated by using relativistic all-electron density functional theory with generalized gradient approximation. A number of new isomers are obtained for neutral MnAu(n) (n = 1-16) clusters to probe the structural evolution. The two-dimensional (2D) to three-dimensional (3D) transition occurs in the size range n = 7-10 with manifest structure competitions. From size n = 13 to n = 16, the MnAu(n) prefers a gold cage structure with Mn atom locating at the center. The relative stabilities of the ground-state MnAu(n) clusters show a pronounced odd-even oscillation with the number of Au atoms. The magnetic moments of MnAu(n) clusters vary from 3 μ(B) to 6 μ(B) with the different cluster size, suggesting that nonmagnetic Au(n) clusters can serve as a flexible host to tailor the dopant's magnetism, which has potential applications in new nanomaterials with tunable magnetic properties.     

Structures and electronic properties of small FeB n (n=1-10) clusters

The geometries, stabilities, electronic properties, and magnetism of FeB(n) clusters up to n=10 are systematically studied with density functional theory. We find that our optimized structures of FeB(2), FeB(3), FeB(4), and FeB(5) clusters are more stable than those proposed in previous literature. The results show that it is favorable for the Fe atom to locate at the surface, not at the center of the cluster, and that FeB(4) and FeB(9) clusters exhibit high stability. For all the FeB(n) clusters studied, we find the charge transfer from Fe to B site and the coexistence of ionic and covalent bonding characteristics. The computed total magnetic moments of the lowest-energy structures oscillate with the cluster size and are quenched at n=4, 6, 8, and 10.     

First-principles study of electronic and magnetic properties of Co(n)Mn(m) and Co(n)V(m) (m + n < or = 6) clusters

The electronic and magnetic properties of small Co(n)Mn(m) and Co(n)V(m) (m + n < or = 6) clusters are systematically studied using density functional theory. The results show that Co and V atoms prefer to aggregate in Co-Mn and Co-V clusters, respectively. Significant magnetic moment enhancement in Co-Mn clusters with Mn doping and reduction in Co-V clusters with V doping are found, consistent with experiment results for larger clusters [Phys. Rev. Lett. 2007, 98, 113401]. The results are discussed by analyzing the magnetic coupling type and local magnetic moment on each atoms. Density of states and vertical ionization potentials are calculated and show cluster size dependent behavior.     

Transition metal-boron complexes BnM: from bowls (n = 8-14) to tires (n = 14)

Transition metal-boron complexes BnM have been predicted at density functional theory level to be molecular bowls (n = 8-14) hosting a transition metal atom (M) inside or molecular tires (n = 14) centered with a transition metal atom. Small Bn clusters prove to be effective inorganic ligands to all the VB-VIIIB transition metal elements in the periodic table. Density functional evidences obtained in this work strongly suggest that bowl-shaped fullerene analogues of Bn units exist in small BnM complexes and the bowl-to-tire structural transition occur to the first-row transition metal complexes BnM (M = Mn, Fe, Co) at n = 14, a size obviously smaller than n = 20 where the 2D-3D structural transition occurs to bare Bn. The half-sandwich-type B12Cr (C3v), full sandwich-type (B12)2Cr (D3d), bowl-shaped B14Fe (C2), and tire-shaped B14Fe (D7d) and B14Fe- (C7v) are the most interesting prototypes to be targeted in future experiments. These BnM complexes may serve as building blocks to form extended boron-rich BnMm tubes or cages (m > or = 2) or as structural units to be placed inside carbon nanotubes with suitable diameters.     

Bonding of benzene with excited States of Fe7

The interaction between high-spin Fe7 clusters and a benzene molecule was studied using the BPW91/6-311++G(2d,2p) method. The Fe7-C6H6 ground state has a T-shaped structure, similar to that of the benzene dimer, and a multiplicity M = 2S + 1 = 19 (S = total spin). The carbon atoms are bonded to a single equatorial iron atom, which experiences a dramatic decrease in its magnetic moment, from 3.1 to -0.8 mu(B); the magnetic moments of other Fe atoms are larger than those in the ground-state Fe7 cluster. Such unexpected magnetic behavior of the cluster is crucial for adsorption of benzene.     

Stability and magnetic properties of transition metal atoms endohedral BnNn (n=12-28) cages

First-principles calculations have been conducted to systemically investigate the stability and magnetic properties of 3d and 4d transitional-metal (TM) atoms doped in the BnNn (n=12,16,20,24,28) cages. Among those cages, the B24N24 is the optimal one for encapsulating 3d and 4d TM atoms according to the computed heat of formation. Inside B24N24 cage, 3d and 4d TM dopants belonging to the same group in the Periodic Table exhibit similar magnetic behaviors. Most of the 3d and 4d TM atoms remain magnetic after doped in the B24N24 cage except for Ni, Zr, and Pd. The magnitudes of the remaining moments for 3d (except for Sc, Ti, and V) and 4d dopants are reduced from those of free atoms. The energy gaps are localized at the doped transition metal atoms. Encapsulations of two TM atoms inside the B24N24 cage were also considered.     

Control of magnetic ordering by Jahn--Teller distortions in Nd(2)GaMnO(6) and La(2)GaMnO(6).

The substitution of Ga(3+) into the Jahn--Teller distorted, antiferromagnetic perovskites LaMnO(3) and NdMnO(3) strongly affects both the crystal structures and resulting magnetic ordering. In both compounds the Ga(3+) and Mn(3+) cations are disordered over the six coordinate sites. La(2)GaMnO(6) is a ferromagnetic insulator (T(c) = 70 K); a moment per Mn cation of 2.08(5) mu(B) has been determined by neutron powder diffraction at 5 K. Bond length and displacement parameter data suggest Jahn--Teller distortions which are both coherent and incoherent with the Pnma space group symmetry of the perovskite structure (a = 5.51122(4) A, b = 7.80515(6) A, c = 5.52947(4) A) at room temperature. The coherent distortion is strongly suppressed in comparison with the parent LaMnO(3) phase, but the displacement ellipsoids suggest that incoherent distortions are significant and arise from local Jahn--Teller distortions. The preparation of the new phase Nd(2)GaMnO(6) has been found to depend on sample cooling rates, with detailed characterization necessary to ensure phase separation has been avoided. This compound also adopts the GdFeO(3)-type orthorhombically distorted perovskite structure (space group Pnma, a = 5.64876(1) A, b = 7.65212(2) A, c = 5.41943(1) A at room temperature). However, the B site substitution has a totally different effect on the Jahn--Teller distortion at the Mn(3+) centers. This phase exhibits a Q(2) mode Jahn--Teller distortion similar to that observed in LaMnO(3), although reduced in magnitude as a result of the introduction of Ga(3+) onto the B site. There is no evidence of a dynamic Jahn-Teller distortion. At 5 K a ferromagnetically ordered Nd(3+) moment of 1.06(6) mu(B) is aligned along the y-axis and a moment of 2.8(1) mu(B) per Mn(3+) is ordered in the xy plane making an angle of 29(2) degrees with the y-axis. The Mn(3+) moments couple ferromagnetically in the xz plane. However, along the y-axis the moments couple ferromagnetically while the x components are coupled antiferromagnetically. This results in a canted antiferromagnetic arrangement in which the dominant exchange is ferromagnetic. Nd(2)GaMnO(6) is paramagnetic above 40(5) K, with a paramagnetic moment and Weiss constant of 6.70(2) mu(B) and 45.9(4) K, respectively. An ordered moment of 6.08(3) mu(B) per Nd(2)GaMnO(6) formula unit was measured by magnetometry at 5 K in an applied magnetic field of 5 T.     

A density functional study of YnAl (n=1-14) clusters

The geometries, stabilities, and electronic and magnetic properties of Y(n)Al (n=1-14) clusters have been systematically investigated by using density functional theory with generalized gradient approximation. The growth pattern for different sized Y(n)Al (n=1-14) clusters is Al-substituted Y(n+1) clusters and it keeps the similar frameworks of the most stable Y(n+1) clusters except for Y(9)Al cluster. The Al atom substituted the surface atom of the Y(n+1) clusters for n<9. Starting from n=9, the Al atom completely falls into the center of the Y-frame. The Al atom substituted the center atom of the Y(n+1) clusters to form the Al-encapsulated Y(n) geometries for n>9. The calculated results manifest that doping of the Al atom contributes to strengthen the stabilities of the yttrium framework. In addition, the relative stability of Y(12)Al is the strongest among all different sized Y(n)Al clusters, which might stem from its highly symmetric geometry. Mulliken population analysis shows that the charges always transfer from Y atoms to Al atom in all different sized clusters. Doping of the Al atom decreases the average magnetic moments of most Y(n) clusters. Especially, the magnetic moment is completely quenched after doping Al in the Y(13), which is ascribed to the disappearance of the ininerant 4d electron spin exchange effect. Finally, the frontier orbitals properties of Y(n)Al are also discussed.     

Isolation of the new cubic phases RE4FeGa(12-x)Ge(x) (RE = Sm,Tb; x = 2.5) from molten gallium: single-crystal neutron diffraction study of the Ga/Ge distribution

The compounds RE4FeGa(12-x)Ge(x) (RE = Sm, Tb) were discovered in reactions employing molten Ga as a solvent at 850 degrees C. However, the isostructural Y4FeGa(12-x)Ge(x) was prepared from a direct combination reaction. The crystal structure is cubic with space group Imm, Z = 2, and a = 8.657(4) A and 8.5620(9) A for the Sm and Tb analogues, respectively. Structure refinement based on full-matrix least squares on F(o)2 resulted in R1 = 1.47% and wR2 = 4.13% [I > 2(I)] for RE = Sm and R1 = 2.29% and wR2 = 7.12% [I > 2(I)] for RE = Tb. The compounds crystallize in the U4Re7Si6 structure type, where the RE atoms are located on 8c (1/4, 1/4, 1/4) sites and the Fe atoms on 2a (0, 0, 0) sites. The distribution of Ga and Ge in the structure, investigated with single-crystal neutron diffraction on the Tb analogue, revealed that these atoms are disordered over the 12d (1/4, 0, 1/2) and 12e (x, 0, 0) sites. The amount of Ga/Ge occupying the 12d and 12e sites refined to 89(4)/11 and 70(4)/30%, respectively. Transport property measurements indicate that these compounds are metallic conductors. Magnetic susceptibility measurements and M?ssbauer spectroscopy performed on the Tb analogue show a nonmagnetic state for Fe, while the Tb atoms carry a magnetic moment corresponding to a mu(eff) of 9.25 mu(B).     

(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.     

First-principle Study of AunSc (n=2～13) Clusters

The geometries, stabilities, electronic, and magnetic properties of Au_nSc clusters have been systematically investigated by density functional theory. The lowest energy structures of Au_nSc favor planar structure and the doped Sc atom does not disturb the frame of Au_nclusters with n≤11. For n≥12, Sc atom is fully encapsulated by the Au cages. From theanalysis of the second-order energy difference, the fragmentation energies, vertical ionizationpotential, vertical electron affinity, and HOMO-LUMO gap, the clusters with odd Au atoms possess relatively higher stabilities than their neighbor size. The doping of Sc atom can greatly improve the stability and change the sequence of chemical activity for Au_n. For n≤11, the total magnetic moments of Au_nSc appear the alternation between 0.00 and 1.00 μB. The total magnetic moments are quenched when Sc is trapped into the Au cages with n≥12.     

FMBen（FM=Fe,Co,Ni;n=1-12）团簇结构和电子性质

采用密度泛函理论中的广义梯度近似对FMBen(FM=Fe,Co,Ni;n=1-12)团簇的几何构型进行优化,并对能量、频率和磁性进行了计算,同时考虑了电子的自旋多重度.结果表明,纯铍团簇的幻数是由电子的壳层模型确定,而FMBen团簇的幻数主要由几何效应来解释;掺杂铁磁性的过渡金属(Fe,Co,Ni)提高了纯团簇的稳定性.二阶能量差分表明FMBen(FM=Fe,Co,Ni)的幻数分别为5,10;5,10;4,10.通过对磁性质的研究发现掺杂不同的过渡金属时,磁矩出现了不同的变化规律.     

LMTO法研究NdFe10M2的电子结构与磁性能

采用能带论中线性Ｍｕｆｆｉｎ－ｔｉｎ轨道方法,计算了ＮｄＦｅ１０Ｍ２（Ｍ＝Ｔｉ,Ｖ,Ｃｒ,Ｍｎ,Ｍｏ,Ｗ）及渗Ｎ和Ｃ原子后材料的电子结构,得到了相应的总体态密度和各晶位的局域态密度,并由净自旋数得出了相应的磁矩及其变化,计算值与实验值相符合。     

Geometries and magnetisms of the Zr(n) (n=2-8) clusters: the density functional investigations

The geometries, stabilities, and electronic and magnetic properties of small-sized Zr(n) (n=2-8) clusters with different spin configurations were systematically investigated by using density functional approach. Emphasis is placed on studies that focus on the total energies, equilibrium geometries, growth-pattern behaviors, fragmentation energies, and magnetic characteristics of zirconium clusters. The optimized geometries show that the large-sized low-lying Zr(n) (n=5-8) clusters become three-dimensional structures. Particularly, the relative stabilities of Zr(n) clusters in terms of the calculated fragmentation energies and second-order difference of energies are discussed, exhibiting that the magic numbers of stabilities are n=2, 5, and 7 and that the pentagonal bipyramidal D(5h) Zr(7) geometry is the most stable isomer and a nonmagnetic ground state. Furthermore, the investigated magnetic moments confirm that the atomic averaged magnetic moments of the Zr(n) (n not equal to 2) display an odd-even oscillation features and the tetrahedron C(s) Zr(4) structure has the biggest atomic averaged magnetic moment of 1.5 mu(B)/at. In addition, the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital gaps indicate that the Zr(n) (n=2 and 7) clusters have dramatically enhanced chemical stabilities.     

FMBen(FM=Fe,Co, Ni; n=1-12)团簇结构和电子性质

采用密度泛函理论中的广义梯度近似对FMBen(FM=Fe, Co, Ni; n=1-12)团簇的几何构型进行优化, 并对能量、频率和磁性进行了计算, 同时考虑了电子的自旋多重度. 结果表明, 纯铍团簇的幻数是由电子的壳层模型确定, 而FMBen团簇的幻数主要由几何效应来解释; 掺杂铁磁性的过渡金属(Fe, Co, Ni)提高了纯团簇的稳定性. 二阶能量差分表明FMBen(FM=Fe, Co, Ni)的幻数分别为5, 10; 5, 10; 4, 10. 通过对磁性质的研究发现掺杂不同的过渡金属时, 磁矩出现了不同的变化规律.