Ultralowthermal conductivity draws great attention in avariety of fields of applications such as thermoelectrics and thermal barrier coatings.H erein, the crystal structure and transport properties of Cu 4 TiSe 4 are reported. Cu 4 TiSe 4 is au nique example of an on-toxic and low-cost material that exhibits al attice ultra-low thermal conductivity of 0.19 Wm À1 K À1 at room temperature.T he main contribution to the unusually low thermal conductivity is connected with the atomic lattice and its dynamics.T his ultralow value of lattice thermal conductivity (k L )c an be attributed to the presence of the localized modes of Cu, which partially hybridizew ith the Se atoms,w hich in turn leads to avoidance of crossing of acoustic phonon modes that reach the zone boundary with ar educed frequency.L ike ap honon glass electron crystal, Cu 4 TiSe 4 could also open ar oute to efficient thermoelectric materials,even, with chalcogenides of relatively high electrical resistivity and al arge band gap,p rovided that their structures offer as ublattice with lightly bound cations.
A nonstoichiometric line phase, Rh 3 Cd 5−δ (δ ∼ 0.56), is found in close vicinity to RhCd and structurally characterized by single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy. The compound crystallizes in the cubic space group Im3m (No. 229) with lattice constant a = 6.3859(9) Å and represents a 2 × 2 × 2 superstructure of RhCd, which accommodates a vacancy concentration of nearly 6% in its crystal structure. The first-principles electronic structure calculation on a hypothetical ordered configuration of Rh 3 Cd 5−δ reveals that Rh−Cd heteroatomic interaction plays a major role in the stability of the compound. A combination of the total energy, formation energy, and crystal orbital Hamilton population calculations on hypothetical model configurations establishes that the compound upholds an optimum vacancy concentration in the Cd2a (Cd1) site for the stability of the phase.
Two new metal complexes namely [Zn2(LH)2(N3)4] (1) and [Cu(L)(N3)] (2) have been derived from a Schiff base ligand, (E)-2-(((2-(piperidine-2-yl)ethyl)imino)methyl)phenol (HL) employing azide as the secondary anionic residue. Single crystal structural...
A new ternary compound CuZnSb was synthesized by high temperature solid state synthesis and characterized by single crystal X-ray diffraction and energy dispersive X-ray analysis. The ternary CuZnSb crystallizes in the tetragonal crystal system with the space group P4/ nmm (129), and its unit cell contains 10 atoms which are distributed over 4 independent crystallographic positions. The structure is built up with [CuSb] slabs that correspond to the unit cells of CuSb and planar 4 nets of Zn atoms. The planar nets of Zn atoms are interspersed between two adjacent [CuSb] slabs. The structure can be viewed as alternating units of CuSb and CsCl type β'-brass (CuZn) structures in the [001]. An unusual atomic ordering of two neighboring transition metals Cu and Zn is observed and is confirmed by first principle calculations. The atomic ordering of Cu and Zn is retained from binary β'-brass structure (CuZn) to ternary CuZnSb. Total energy calculations confirmed the experimental model of Cu/Zn ordering to be the most stable in the structure of CuZnSb. The calculated density of states (DOS) and crystal orbital Hamiltonian population (COHP) explain the stability and bonding characteristics in the structure of CuZnSb. The implication of the persistent Cu/Zn ordering in ternary phases for materials design is emphasized.
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