Pressure-induced changes in electronic and vibrational properties of LaS

The high-pressure induced phase transition in LaS has been investigated by means of first-principles calculations, and density-functional linear-response theory. A pressure-induced soft-acoustic phonon mode is identified at 30?GPa, which is in favourable agreement with the measured pressure-induced phase transition in LaS from the rocksalt to the CsCl structure. Phonon calculations reveal that pressure-induced instabilities of the transverse acoustic modes at the [?00] and [??0] directions are responsible for the phase transition. Furthermore, it is found that a decrease of bonding for S-p bonds and an increase of anti-bonding for La-d bonds significantly weakens the stability of the rocksalt phase of LaS under pressure, and hence inducing the structural phase transformation.     

Ab-initio study of the structural,electronic, elastic and vibrational properties of HfX (X = Rh,Ru and Tc)

The structural, elastic, electronic and phonon properties of HfX (X = Rh, Ru and Tc) in the caesium-chloride phase have been investigated using the density functional theory within the generalized gradient approximation. The optimized lattice constant (a₀), bulk modulus (B) and the elastic constants (C_ij) are evaluated. The results are in a good agreement with the available experimental and theoretical data in the literature. Electronic band structures and densities of states have been derived for these compounds. The present band structure calculations indicate that the phases of caesium-chloride HfX (X = Rh, Ru and Tc) compounds are metals. Phonon dispersion curves and their corresponding total and projected density of states have been obtained using the direct method. The phonon spectra suggest that these compounds are dynamically stable in the caesium-chloride phase.     

Thermal effects on infiltration of a solubility-sensitive volume-memory liquid

As the ion density at a solid–liquid interface changes, the interfacial tension varies accordingly, which can lead to a large energy density output, particularly when amplified by the high specific surface area of a nanoporous material. This concept is validated by the results of a controlled-temperature infiltration experiment on a hydrophobic zeolite immersed in a saturated aqueous solution of sodium acetate. As the temperature changes, the sodium acetate concentration varies significantly, which in turn causes a variation in infiltration pressure. Since the infiltration and defiltration are reversible, under the working pressure, this system exhibits a volume memory characteristic, with a non-monotonic temperature–volume relationship.