The electronic structures,chemical bonding,elastic and optical properties of the ternary stannide phase Na2MgSn were investigated by using density-fimctional theory（DFT） within generalized gradient approximation（GGA）.The calculated energy band structures show that Na2MgSn is an indirect semiconductor material with a narrow band gap 0.126 eV.The density of state（DOS）and the partial density of state（PDOS） calculations show that the DOS near the Fermi level is mainly from the Na 2p,Mg 3p and Sn5 p states.Population analysis suggests that there are strongly bonded Mg-Sn honeycomb layers in Na2MgSn.Basic physical properties,such as lattice constant,bulk modulus,shear modulus,elastic constants c（ij） were calculated.The elastic modulus E and Poisson ratio v were also predicted.The results show that Na2MgSn is mechanically stable soft material and behaves in a brittle manner.Detailed analysis of all optical functions reveals that Na2MgSn is a better dielectric material,and reflectivity spectra show that Na2MgSn promise as good coating materials in the energy regions 6.24-10.49 eV.
EuMg6Sn3.67 has been synthesized by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction study. EuMg6Sn3.67 crystallizes in hexagonal space group P63/m （No. 176） with a = 11.7259（4）, c = 4.5507（2） A, V= 541.88（4）A3 Z = 2, Mr = 734.60, Dc= 4.502 g/cm3, μ = 14.348 mm-1, F（000） = 638, the final R = 0.0128 and wR = 0.0378 for 464 observed reflections with 1 〉 2σ-（1）. EuMg6Sn3.67 is closely related to the Ba2Mg2GeT.33 structure type and features a three-dimensional [Mg6Sn3.67] framework with one-dimensional hexagonal tunnels along the c-axis occupied by the Eu atoms. Electronic structure calculation indicates that the title compound is metallic.
A new tetragonal phase of LunSnl0 is obtained from high temperature reaction of the pure elements in a welded tantalum tube. Its crystal structure was established by single-crystal X-ray diffraction. Lu11Sn10 crystallizes in the tetragonal space group 14/mmm （No. 139） with a = 11.2953（18）, c = 16.424（4） A, V= 2095.5（7）A3, Z= 4, Mr = 3111.57, Dc = 9.863 g/cm^3, p = 62.897 -1 mm , F（000） = 5124, and the final R = 0.0348 and wR = 0.0894 for 706 observed reflections with 1 〉 2σ（I）. The structure of LullSnl0 may be derived from the HonGel0 structural type. It is isostructural with DyllSn10, featuring a three-dimensional （3D） framework composed of [Sn4] squares and [Sn2] dimers interlinked via Sn-Sn bonds with two types of one-dimensional （1D） tunnels along the c-axis, which are occupied by isolated Sn atoms, [Sn2] dimers and all the Lu atoms Band structure calculation based on density functional theory method indicates that LUllSn10 is metallic.
A new intermetallic compound,Tb3Co4Sn13,has been synthesized by solid-state reaction of the corresponding pure elements in a welded tantalum tube at high temperature.Its crystal structure was established by single-crystal X-ray diffraction.Tb3Co4Sn13 crystallizes in cubic,space group Pm3n（No.223） with a = 9.5072（2） ,V = 859.33（3） 3,Z = 2,Mr = 2255.45,Dc = 8.717 g/cm3,μ = 34.369 mm-1,F（000） = 1906,and the final R = 0.0140 and wR = 0.0312 for 199 observed reflections with I〉 2σ（I）.The structure of Tb3Co4Sn13 belongs to the Yb3Rh4Sn13 type.It is isostructural with RE3Co4Sn13（RE = La,Ce）,featuring a 3D [Co4Sn12] framework based on [CoSn6] trigonal prisms.The [CoSn6] trigonal prisms are interconnected via corner-sharing and Sn-Sn bonds to form a 3D [Co4Sn12] framework.The other Sn and Tb atoms are located in the spacers of the 3D framework.Band structure calculations indicate that Tb3Co4Sn13 is metallic.
A new polar intermetallic compound, Eu3Sn5, has been synthesized by solid-state reaction of the corresponding pure elements in a stoicbiometric ratio in a welded tantalum tube at high temperature. Its crystal structure was established by single-crystal X-ray diffraction. EuaSn5 crystallizes in orthorhombic, space group Cmcm with a = 10.466（11）, b = 8,445（8）, c = 10.662（12）/k, V = 942.4（17）A^3, Z = 4, Mr = 1049.33, De= 7.396 g/cm^3, ,μ = 32.578 mm^-1, F（000） = 1756, the final R = 0.0236 and wR = 0.0472 for 535 observed reflections with I 〉 2σ（I）. Its structure belongs to the modified Pu3Pd5 type. It is isostructural with SraSn5 and Ba3Sn5, featuring [Sn5] square pyramidal clusters described as “arachno” according to the Wade-Mingos electron counting rules. The europium cations are located at the voids between the square pyramidal clusters. Results of the extended Htickel band structure calculations indicate that Eu3Sn5 is metallic.
