NMR and high-resolution x-ray diffraction of several lithium-doped fullerides LixC60 show that the stoichiometry x512 represents a stable Li doping for a high symmetry C60-like phase, which might extend to much larger x. Li12C60 is fcc at high temperature, and it distorts to tetragonal upon cooling. We have evidence from C NMR that the C60 units are static in the tetragonal phase at least up to...

The possible role of the van Hove singularity (vHs) in stabilizing the low-temperature orthorhombic (LTO) phase transition in La 2−x Sr x CuO 4 (LSCO) is discussed. It is found that the vHs can drive a structural distortion in two different ways, either due to spin-orbit coupling or to dynamic Jahn-Teller (JT) effects. This paper discusses the latter effect in some detail. It is shown that a mo...

We report the dynamics of the structure of CaSiO3 perovskite from ab initio molecular dynamics (AIMD) calculations at high pressure (P up to 130 GPa) and high temperature (T up to 5000 K). Our calculations indicate three separate stability fields: orthorhombic, tetragonal and cubic, with the tetragonal phase dominating the pressure and temperature region between room temperature and 4000 K. The...

We performed systematic studies of the combined effects of annealing/quenching temperature (TA/Q) and T=Ni, Rh substitution (x) on the physical properties of Ca(Fe1−xTx)2As2. We constructed two-dimensional, TA/Q-x phase diagrams for the low-temperature states for both substitutions to map out the relations between ground states and compared them with that of Co substitution. Ni substitution, wh...

High-temperature phases of hafnium dioxide have exceptionally high dielectric constants and large bandgaps, but quenching them to room temperature remains a challenge. Scaling the bulk form to nanocrystals, while successful in stabilizing the tetragonal phase of isomorphous ZrO2, has produced nanorods with a twinned version of the room temperature monoclinic phase in HfO2. Here we use in situ h...

TheZrO2-based materials are practically important as the thermal barrier coatings(TBC) for high temperature gas turbines, due to their low thermal conductivity, hightemperature thermal stability and excellent interfacial compatibility. Studies of the phaseequilibira, phase transformation, and thermodynamics of the ZrO2-based systems can providethe necessary basic knowledge t...

Raman spectroscopy demonstrates that ,5 nm dimension HfxZr1−xO2 nanocrystals prepared by a nonhydrolytic sol-gel synthesis method are solid solutions of hafnia and zirconia, with no discernable segregation within the individual nanoparticles. Zirconia-rich particles are tetragonal and ensembles of hafnia-rich particles show mixed tetragonal/monoclinic phases. Sintering at 1200 °C produces large...