We synthesized a series of polycrystalline YbCd2−xZnxSb2 (x=0, 0.4, 0.8, 1, 1.2, 1.6, and 2) samples and measured their thermoelectric properties. Thermoelectric figure of merit ZT at 700K is higher than 1.0 for Cd-rich samples (x=0, 0.4, 0.8, and 1.0) and Zn substitute of Cd in YbCd2Sb2 can easily tune carrier concentration and reduce thermal conductivity. When x=0.4, sample exhibits the highest power factor (12–20μWcm−1K−2), the lowest lattice thermal conductivity (1.0Wm−1K−1 at 300K), highest ZT (1.2 at 700K), and best “self-compatibility.” The first principles calculations were performed to study the influences of bonding and electronic structures on physical properties.

Single crystals of Ba(8)Au(5.3)Ge(40.7) [space group Pm(3)n (No. 223), a = 10.79891(8) Å] were prepared by a Bridgman technique. The crystal structure refinement based on single-crystal X-ray diffraction data does not reveal any vacancies in the Au/Ge framework or in the cages. In addition to the ionic bonding between Ba and the anionic framework, a direct interaction between Ba and Au atoms was identified in Ba(8)Au(5.3)Ge(40.7) by applying the electron localizability indicator. As expected by the chemical-bonding picture, Ba(8)Au(5.3)Ge(40.7) is a diamagnet and shows p-type electrical conductivity with a hole carrier concentration of 7.14 × 10(19) cm(-3) at 300 K and very low lattice thermal conductivity of ≈0.6 W m(-1) K(-1) at 500 K. The thermoelectric figure of merit ZT of single crystals of Ba(8)Au(5.3)Ge(40.7) attains 0.3 at 511 K and reaches 0.9 at 680 K in a polycrystalline sample of closely similar composition. This opens up an opportunity for tuning of the thermoelectric properties of materials in the Ba-Au-Ge clathrate system by changing the chemical composition.

Protein flexibility is inherent to protein structural behavior. Experimental evidence for protein flexibility is extensive both in solution and in the solid state. A major question is whether the flexibility observed in enzymes is simply an inherent property of proteins that must always be borne in mind or is essential for catalysis or substrate binding. The temperature factors or B-values, as determined crystallographically, are linearly related to the mean square displacement of an atom and give an indication of atomic flexibility in the crystalline state. In this paper, we describe the frequency distributions of the normalized B-factor (B'-factor) for the active site and non-active site residues in the selected 69 apo-enzymes. This analysis was performed over the entire sequences and for different structural subsets defined by the three-dimensional structure of proteins, as alpha-helices, beta-structures and coil conformation and buried and non-buried residues. The results show that in all cases, the active site residues predominantly occur in region of low B'-factor and the non-active site residues have a tendency to exist in the high B'-factor region. This observation suggests that the active site residues, in general, are less flexible than the non-active site residues and therefore the vibrational and the fast collective motions of the C(alpha) atoms of proteins appear not to have clear biological significance.

Single-phase KgSn25 is synthesized from the elements on annealing below 400 "C. The phase is somewhat nonstoichiometric, and the lattice constant also depends on thermal history. The structure was solved for K7.4(1)-Sn25 (s.g. P4132, Z = 4, a = 16.294(5) A, RIR, = 4.013.6% for 833 observed reflections and 55 parameters).The new structure type contains pentagonal dodecahedra of tin that share three pentagonal faces with like members and are also interconnected to another cage through a single exo bond. Tin-tin distances are very similar to those in gray tin and in RbgSw. The three types of potassium ions are (1) encapsulated in each Sn20 cage, (2) bonded in tin octahedra between clusters, and (3) somewhat disordered in channels through the tin network. Eight tin atoms per formula unit are three-bonded, the remainder four-bonded, and the ideal compositon Kg.oSnz5 is, appropriately, a diamagnetic semiconductor. An analogous compound does not form in the binary rubidium or cesium systems. The crystal structures of the isostructural RbgSw.6(1) and K1,6(~)Cs6,4~2)Sw.0(1) were also refined (Pm3n, Z = 1, a = 12.054(1), 12.084(1) A, RIR, = 7.616.7, 6.615.7, respectively). These are defect members of the clathrate-I Ag(H20)46 type structure with one-third random vacancies at the 6c positions and classical Zintl phases. K g S u was shown to be a diamagnetic semiconductor.

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