First-principles study of high-temperature superconductivity in ScXH8 (X = Y, La, Zr, Mg, Ca, Hf) compounds under high pressure

Contributors. Preface. Acknowledgements. Evangelos Anastassakis (1938-2000). Material Synthesis at High Pressures. Stabilization of Unusual Oxidation States of Transition Metals in Oxygen Lattices: Correlations with the Induced Electronic Phenomena G. Demazeau. Synthesis and Properties of Low dimensional F-Element Chalocogenide Compounds P.K. Dorhout, C.R. Evenson, IV. Synthesis and High-Pressure Behavior of C6N9H3*HCl: A graphitic material with a two-dimensional C-N network G.H. Wolf, et al. Plasma Polymerization of Thin Films Using Aniline and p-Xylene Precursors A. Dumitru, et al. Pressure-Induced Phase Transitions. Compressibility, Pressure-Induced Amorphisation and Thermal Collapse of Zeolites G.N. Greaves. Pressure-induced H-transfers in the networks of hydrogen bonds A. Katrusiak. The Light Elements at High Pressure, in Layered Form, and in Combination N.W. Ashcroft. Pressure-induced Phase Transitions in GaSe-, TlGaSe2- and CdGa2S4-type Crystals K.R. Allakhverdiev. Influence of Pressure on the Physical Properties of Chain TlSe-type Crystals K.R. Allakhverdiev, S.S. Ellialtiogammalu. Impendance Spectroscopy at Super High Pressures A.N. Babushkin, et al. Optical Properties of A2CuCl4 Layer Perovskites under Pressure: Structural Correlations F. Rodriguez, et al. The Effect of Pressure-Induced Collapse of Correlation and Hund's Rules on Structure and Electronic Properties of Transition-Metal Compounds M. Paz-Pasternak, et al. Pressure Tuning of Condensation and Ordering of Charge-Transfer Strings H. Cailleau, et al. From Ferroelectric to Quantum Paraelectric: Ktal-xNbxO3(KTN), a Model System G.A.Samara. Molecular Solids Under High Pressures. Quartz like phases in CO2 at very high pressure from ab initio simulations R. Ahuja, et al. Progress in Experimental Studies of Insulator-Metal Transitions at Multimegabar Pressures R.J. Hemley, et al. Solid Oxygen as Low dimensional System by Spectroscopic Studies A. Brodyanski, et al. Evolution of Rotational Spectrum in Solid Hydrogen with Pressure: Implications for Conversion and other Properties M.A. Strzhemechny. An Influence of the Pressure on Metastability of the HCP Phase of Solid Nitrogen B. Kuchta, et al. Semiconductors, 2-D Impurity States, Quantum Dots. X-ray Study of Strain Relaxation in Heteroepitaxial Layers of Semiconductors Annealed under High Hydrostatic Pressure J. Bak-Misiuk. Application of High Temperature-Pressure Treatment for Investigation of Defect Creation in Basic Materials of Modern Micro-electronics: Czochralski Silicon and Solicon Containing Films A. Misiuk. Pressure-induced Phase Transformations in Semiconductors under Contact Loading V. Domnich, Y. Gogotsi. Far-Infrared Spectroscopy of Quasi-2D Impurity States in Semiconductor Nanostructures under High Hydrostatic Pressure B.A. Weinstein, et al. Probing the Effects of Three-Dimensional Confinement on the Electronic Structure of InP under Hydrostatic Pressure C.S. Menoni, et al. Pressure Studies in InGaN/GaN Quantum Wells D. Patel, et al. Superconductivity. What High Pressure Studies Have Taught Us about High-Temperature Superconductivity J.S. Schilling. Anisotropic Low-Dimensional Superconductors Close to an Electronic Topological Transition G.G.N. Angilella, et al. Pressure-Induced Superconducting Phase Separation in Oxygen-Doped La2-xSrxCuO4+&dg

As a step toward resolving current discrepancies among ultrahigh-pressure melting curves obtained with the laser-heated diamond cell, we critically evaluate two aspects of the experiments that require further examination: (i) the criteria used to detect that melting has taken place, and (ii) the methods employed for measuring spatially variable temperatures. A review of recent efforts illustrates how defining reliable melting criteria remains problematical in many experiments, whereas current and prospective advances in imaging spectroradiometry can yield robust methods for determining the temperature distribution within the laser-heated diamond cell.

A first-principle study of Os-based compounds: Electronic structure and vibrational properties

New Cage-Like Cerium Trihydride Stabilized at Ambient Conditions

A simplified analytical model of the effect of high pressure on the critical temperature and other thermodynamic properties of superconducting systems is developed using the general conformal transformation method and group-theoretical arguments. Relationships between the characteristic ratios { {mathcal R} }_{1}equiv 2{rm{Delta }}(0)/{T}_{{rm{c}}} and { {mathcal R} }_{2}equiv {rm{Delta }}C({T}_{{rm{c}}})/{C}_{{rm{N}}}({T}_{{rm{c}}}) and the stability of the superconducting state is discussed. Including a single two-parameter fluctuation in the density of states, placed away from the Fermi level, stable solutions determined by { {mathcal R} }_{1} are found. It is shown that the critical temperature Tc(p), as a function of high external pressure, can be predicted from experimental data, based on the values of the two characteristic ratios, the critical temperature, and a pressure coefficient measured at zero pressure. The model can be applied to s-wave low-temperature and high-temperature superconductors, as well as to some novel superconducting systems of the new generation. The problem of emergence of superconductivity under high pressure is explained as well. The discussion is illustrated by using experimental data for superconducting elements available in the literature. A criterion for compatibility of experimental data is formulated, allowing one to identify incompatible measurement data for superconducting systems for which the maximum or the minimum critical temperature is achieved under high pressure.

The discovery of high-temperature superconductivity near 80 K in bilayer nickelate La3Ni2O7 under high pressures has renewed the exploration of superconducting nickelate in bulk materials. The extension of superconductivity in other nickelates in a broader family is also essential. Here, we report the experimental observation of superconducting signature in trilayer nickelate La4Ni3O10 under high pressures. By using a modified sol-gel method and post-annealing treatment under high oxygen pressure, we successfully obtained polycrystalline La4Ni3O10 samples with different transport behaviors at ambient pressure. Then we performed high-pressure electrical resistance measurements on these samples in a diamond-anvil-cell apparatus. Surprisingly, the signature of possible superconducting transition with a maximum transition temperature (T c) of about 20 K under high pressures is observed, as evidenced by a clear drop of resistance and the suppression of resistance drops under magnetic fields. Although the resistance drop is sample-dependent and relatively small, it appears in all of our measured samples. We argue that the observed superconducting signal is most likely to originate from the main phase of La4Ni3O10. Our findings will motivate the exploration of superconductivity in a broader family of nickelates and shed light on the understanding of the underlying mechanisms of high-T c superconductivity in nickelates.

Elastic anisotropies and thermodynamic properties of metal dodecborides under high pressure

First-principles study on structural, elastic and thermodynamic properties of ZrxNb1-x alloys under high pressure

First-principles study of stability, electronic properties and anisotropic elasticity of Al3M (M=Ti, Ta, V, Nb, Hf) intermetallic compounds

Laser ablation of manganite thin films monitored by in situ RHEED

I have been given the task of summarizing the achievements of the Oji Seminar on the `Quest for New Physical Phases under Extreme Conditions'. This is an enormous task and I consider it as impossible to attempt to summarize, in a few words, the status of a seminar which is, itself, a reflection of a rapidly developing field which is highly active, as is obvious from the 37 lectures that were given, and from the more than 20 posters. And it is a field which is so diverse and so dynamic that within the scope of this summary it is impossible to mention all of the important recent developments, and it is even more futile to try to define emerging areas of opportunities. Recent history teaches us that new discoveries come unexpectedly as a result of excellent work by researchers, and not as a result of careful planning by committees or in seminar summaries. An illuminating example of this in the context of the seminar to which this Special Issue is devoted is the exciting progress in the search for metallic hydrogen. Exactly four years ago I listened during the Oji Seminar on `Elementary Processes in Dense Plasmas' to a beautiful review lecture on the long history of searches for the metallization of solid hydrogen under static pressures at low temperatures, presented by Russel Hemley. On the basis of the experimental progress that he described, I speculated at that time that we could expect solid hydrogen to become an alkali metal within five to ten years. But despite an unrelenting experimental assault at pressures up to 340 GPa (Narayana et al 1998), dense solid hydrogen has so far defied all attempts at metallization. The actual experimental status at the time of the present seminar was critically analysed in the pedagogically beautiful lectures of Russel Hemley and Isaac Silvera. They emphasized that to date, most probes of a possible metallic state have been optical, and for sceptics the only rigorous criterion for differentiating between a metal and a nonmetal is to measure the static conductivity.

As one of the 25 physics challenges in this century, high-temperature superconductivity has been of concern for a long time. According to BCS theory, superconductivity is possible if three conditions are met, which are high-frequency phonons, strong electron–phonon coupling, and a high density of states. In theory, the metallic state of hydrogen and hydride under high pressure can satisfy the above conditions. Several binary hydride systems have been experimentally proved to be high-temperature superconductors (HTSs) at high pressure. Ternary hydrides can be regarded as the doping of binary hydrides, which have broad prospects. At present, in both experimental and theoretical research, ternary hydrides are the record holder for the highest superconducting critical temperature ([Formula: see text] which is 287 K in C–H–S system, and 473 K in Li–Mg–H system, respectively. This review will systematically describe the research status of superconductivity on ternary hydride at high pressure. Relevant theoretical research was classified according to different binary hydride doping systems. The experimental research was then introduced. In terms of experimental research, we focus on the latest research of C–S–H and La–Y–H HTSs, and overview the subsequent studies about high [Formula: see text] of C–S–H system.

Recent studies suggest that the tetragonal phase of the Ruddlesden-Popper (RP) bilayer nickelate, La3Ni2O7 or La2PrNi2O7, which is stabilized under high pressures, is responsible for high-temperature superconductivity (HTSC). In this context, realization of the tetragonal phase at ambient pressure could be a rational step to achieve the goal of ambient-pressure HTSC in the nickelate system. By employing the concept of Goldschmidt tolerance factor, we succeed in stabilizing the tetragonal phase by aluminum doping together with post annealing under moderately high oxygen pressure. X-ray and neutron diffractions verify the tetragonal I4/mmm structure for the post-annealed samples La3Ni2−xAlxO7−δ (0.3 ≤ x ≤ 0.5). The Al-doped samples, including the tetragonal ones, show semiconducting properties, carry localized magnetic moments, and exhibit spin-glass-like behaviors at low temperatures, all of which can be explained in terms of charge carrier localization. Furthermore, high-pressure resistance measurements on post-annealed samples reveal that even a low Al doping (x = 0.05) suppresses superconductivity almost completely. This work gives information about the effect of nonmagnetic impurity on metallicity as well as superconductivity in bilayer nickelates, which would contribute to understanding the superconducting mechanism in RP nickelates.

First-principles calculations for CdSe and CdTe nanostructures were carried out to study their mechanical properties and band structure under the uniaxial pressure range of 0 to 50GPa. It was presumed that the CdSe and CdTe nanostructures exist in the zinc-blende phase under high pressure. The mechanical properties, such as elastic constants, bulk modulus, shear modulus and Young?s modulus, were explored. Furthermore, Cauchy pressure, Poisson?s ratio and Pugh?s criterion were studied under high pressure for both CdSe and CdTe nanostructures, and the results show that they exhibit ductile property. The band structure studies of CdSe and CdTe were also investigated. The findings show that the mechanical properties and the band structures of CdSe and CdTe can be tailored with high pressure.

MgO is one of the most abundant minerals in the Earth’s interior, and its structure and properties at high temperature and pressure are important for us to understand the composition and behavior in the deep Earth. In the present work, first-principles molecular dynamics calculations were performed to investigate the pressure-induced structural evolution of the MgO melts at 4000 K and 5000 K. The results predicted the liquid–solid phase boundaries, and the calculated viscosities of the melts may help us to understand the transport behavior under the corresponding Earth conditions.