Constant electrical resistivity of Zn along the melting boundary up to 5 GPa

We measured the electrical resistivity of high purity Zn along the melting boundary, up to 5?GPa in a large volume press. The electrical resistivity remained constant on the melting boundary, as predicted in a thermodynamics-based model for simple metals. The effects of pressure and temperature on the electrical resistivity of the solid and liquid states are interpreted in terms of their antagonistic effects on the electronic structure of Zn. Within the error of measurements, our melting temperature data agree well with those of the previous studies. The electronic thermal conductivity was calculated from resistivity data using the Wiedemann–Franz law and shows a decrease with temperature in the solid state and an increase in the liquid state, with a large decrease on melting. Comparison of calculated electronic and measured total thermal conductivities indicates that the electronic component dominates over the phonon component in Zn.     

Electrical resistivity of liquid Sb–Zn alloys

Using the DC four-probe method, temperature dependence of the electrical resistivity (ρ???T) of Sb_{100? x} Zn _x (x?=?25,?40,?50,?57,?61,?80 at%) alloys was investigated in the temperature range of 500–860°C. The results showed that resistivity of each liquid alloy decreased non-linearly with temperature increasing above their liquidus (T _L) until reaching critical temperature, at which the resistivity–temperature coefficients dρ/dT–T converts from negative into positive. The phenomena of liquid phase transformation might relate with the dissociation of covalent bonds, chemical orders and associations in Sb–Zn melts.     

Decreasing electrical resistivity of silver along the melting boundary up to 5 GPa

The electrical resistivity of Ag was experimentally measured at high pressures up to 5?GPa and at temperatures up to ～300?K above melting. The resistivity decreased as a function of pressure and increased as a function of temperature as expected and is in very good agreement with 1 atm data. Observed melting temperatures at high pressures also agree well with previous experimental and theoretical studies. The main finding of this study is that resistivity of Ag decreases along the pressure- and temperature-dependent melting boundary, in conflict with prediction of resistivity invariance. This result is discussed in terms of the dominant contribution of the increasing energy separation between the Fermi level and 4d-band as a function of pressure. Calculated from the resistivity using the Wiedemann–Franz law, the electronic thermal conductivity increased as a function of pressure and decreased as a function of temperature as expected. The decrease in the high pressure thermal conductivity in the liquid phase as a function of temperature contrasts with the behavior of the 1 atm data.     

High pressure ‘cell’ model of compressed methane

Abstract

The Thomas-Fermi method is used to treat self-consistently a model of compressed methane. Two assumptions underlying the treatment are (i) the use of spherical averaging of the proton potential about the C atom in the methane molecule and (ii) the compressed spherical ‘cell’ model. Within this framework, the equilibrium bond length of CH₄ is calculated as a function of cell volume. The free space bond length given by this model is too large, and so results are presented for R_e/R_e(∞) versus cell volume. The volume is finally converted to an estimated pressure using an empirical equation of state. The relevance of the work to ices in planetary material is pointed out.     

Decreasing electrical resistivity of gold along the melting boundary up to 5 GPa

ABSTRACT

The electrical resistivity of gold was experimentally measured at high pressures from 2 to 5?GPa and temperatures ～300?K above melting. The resistivity decreased as a function of pressure and increased as a function of temperature as expected. The temperature dependence of resistivity in the solid and liquid phases are comparable to 1?atm results. The observed melting temperatures at each pressure agree well with previous experimental and theoretical studies. The essential result of this study is that resistivity decreases along the pressure-dependent melting boundary, conflicting with a prediction of invariant behavior as reported in the literature. This result is discussed in terms of the interaction between s and d-bands as both pressure and temperature increase along the melting boundary. The thermal conductivity of gold was calculated from the measured electrical resistivity using the Wiedemann-Franz law. The temperature-induced effect on the thermal conductivity at high temperatures is as expected in both the solid and liquid phase while the pressure-effect shows some variability.     

Electrical resistivity of liquid Bi–Sb alloys

The electrical resistivities of liquid Bi–Sb alloys have been measured by DC four-probe method within Bi-rich composition through a wide temperature range. The distinct anomaly of a hump shape was observed on resistivity–temperature (ρndash;T) curves for liquid Bi–Sb alloys on heating at the relatively high temperatures. These anomalies have revealed the temperature-induced liquid–liquid phase transition in Bi–Sb melts. The DSC results for BiSb20wt% alloy further prove the existence of liquid–liquid transition. Measuring the ρ–T curves first on heating and then on cooling we have found that on cooling the ρ–T curve remained linear. It means that the postulated liquid–liquid transition may be irreversible.     

Electrical resistivity of microinhomogeneous PdMnxFe1−x alloys

The electronic band-structure calculations of the PdFe ferromagnet and the PdMn antiferromagnet performed in this work permit one to conclude that the specific features of the electrical resistivity observed in the ternary PdMn_xFe_1−x alloy system [the deviation from the Nordheim-Kurnakov rule ρ₀(x)∼x(1−x), which is accompanied by a high maximum of residual resistivity (not typical of metals) ρ ₀ ^m ∼220 μΩ cm at x _C∼0.8 and a negative temperature resistivity coefficient in the interval 0.5≤x≤1] are due to the microinhomogeneous (multiphase) state of the alloys and a variation in the band-gap parameter d spectrum caused by antiferromagnetic ordering of a PdMn-type phase. __________ Translated from Fizika Tverdogo Tela, Vol. 44, No. 2, 2002, pp. 193–197. Original Russian Text Copyright ? 2002 by Kourov, Korotin, Volkova.     

Electrical resistivity and superconductivity of amorphous La−Ag alloys

We report on measurements of the electrical resistivity and the superconducting transition temperature of amorphous La–Ag alloys (60–74 at % La) obtained by liquid quenching. The temperature coefficient of the resistivity is always slightly negativ, its value cannot be described well by existing theories.T _c depends linearly on the La content and seems to be not very sensitive to the second alloy constituent.Dedicated to Prof. Dr. W. Buckel on the occasion of his 60th birthday     

Raman spectra of shortite Na2Ca2(CO3)3 compressed up to 8 GPa

A rare mineral shortite, Na₂Ca₂(CO₃)₃, occurs among groundmass minerals in unaltered kimberlites, which suggests its participation in the evolution of kimberlite system. This work presents a high pressure Raman spectroscopic study of natural shortite (Udachnaya east kimberlites) compressed in KBr up to 8?GPa in a diamond anvil cell. At ambient pressure the spectrum contains two strong bands related to symmetric C-O stretching vibrations, four in-plane bending modes, and several low-frequency modes of lattice vibrations. Upon the pressure increase up to 8?GPa, almost all the bands exhibit positive shift with the rate of 1–4?cm^?1/GPa for the lattice modes and 3.6 and 3.9?cm^?1/GPa for the C-O stretching modes. The shifts of Raman modes are rather regular, which implies the absence of reconstructive phase transitions within the studied pressure range, similarly to the behavior of nyerereite, a related carbonate mineral. However, minor anomalies in the ν/P and FWHM/P dependences, observed at about 2?GPa, suggest some rearrangement and disordering of carbonate groups. The obtained data can be used for the estimation of residual pressure in shortite-bearing inclusions in deep-seated minerals.     

Electrical resistivity of Sn–3.5Ag–xBi solder melts

This article reported the temperature dependence of the electrical resistivity (ρ) of liquid Sn–3.5Ag lead-free solder alloy in continuous heating and cooling processes with varying Bi content in the range of 0, 2, 3.5, 5, and 7?wt.% Abnormal transitions can be observed on ρ–T curves, which indicate liquid–liquid structure transition (LLST) occurs in Sn–3.5Ag–xBi melts. Interestingly, unlike the pattern at first heating cycle, the LLST is reversible during subsequent cooling and heating cycles. Sn may play an important role on the reversibility, and Bi has a noticeable influence on the turning temperatures and characteristics during first heating cycle. The transition mechanism is analyzed from the viewpoint of short-range orders.     

Electrical resistivity of alkali metals: Inflation–deflation effect of Fermi surface

The electrical resistivity of liquid alkali metals was calculated using the extended Ziman formula. The possible role of Fermi surface (FS) inflation–deflation (ID) was examined. The calculations reveal that replacing the sharp free electron FS by the expanded (respectively, contracted) one substantially improves the results. This was achieved directly by considering a FS correction factor of the Fermi radius and indirectly by a shift in the muffin-tin zero (MTZ) of the potential from its initial values. Consequently, a correlation between the shift of the MTZ of the potential and the FS factor parameter is revealed. The role of this correlation might contribute to a better understanding of the electron transport properties of other liquid metals and their alloys.     

The βdecay of 147Cs to 147Ba

The ^--decay of ¹⁴⁷Cs to ¹⁴⁷Ba has been studied by means of - and X-ray spectroscopy. A new level scheme of ¹⁴⁷Ba is significantly modified and extended in comparison to the one previously reported. The Advanced Time-Delayed (t) method has been applied to measure half-lives of the 46.2 and 85.4 keV levels in ¹⁴⁷Ba yielding T_1/2 of 510(80) ps and 370(100) ps, respectively. The lifetime results combined with the deduced internal conversion coefficients allowed to assign M1 multipolarity to three transitions. The B(M1) values obtained for the 39.2, 46.2 and 85.4 keV transitions range from 0.017 to 0.043 W.u. and represent typical B(M1) strength in the Ba-Er region. Model calculations using a shell correction approach with the axially deformed Woods-Saxon potential predict for ¹⁴⁷Ba an octupole deformed ground state with ₃ = 0.11.     

Ramp compression of tantalum to 330 GPa

We report on the stress–density and rate-dependent response for Ta, ramp compressed to 330?GPa with strain rates up to 5?×?10⁸?s^?1. We employ temporally shaped laser drives to compress Ta stepped foils over several to tens of nanoseconds. Lagrangian wave-profile analysis reveals a stress–density relationship which falls below the Hugoniot, above the hydrostat, and is consistent with ramp-compression experiments at lower strain rates. We also report on the peak elastic stress prior to plastic deformation as a function of strain rate for laser-driven ramp and shock-compression data spanning the 1–50?×?10⁷?s^?1 strain-rate range. When combined with previously published lower strain data (10¹–10⁷?s^?1), we observe a change in rate dependence, suggesting a transition from thermally activated to defect-limited (phonon drag) dislocation motion occurring at a strain rate of about 10⁵?s^?1.     

Probing the interiors of the ice giants: shock compression of water to 700 GPa and 3.8 g/cm³

Recently, there has been a tremendous increase in the number of identified extrasolar planetary systems. Our understanding of their formation is tied to exoplanet internal structure models, which rely upon equations of state of light elements and compounds such as water. Here, we present shock compression data for water with unprecedented accuracy that show that water equations of state commonly used in planetary modeling significantly overestimate the compressibility at conditions relevant to planetary interiors. Furthermore, we show that its behavior at these conditions, including reflectivity and isentropic response, is well-described by a recent first-principles based equation of state. These findings advocate that this water model be used as the standard for modeling Neptune, Uranus, and "hot Neptune" exoplanets and should improve our understanding of these types of planets.     

Electrical resistivity of dilute (Cr1−xAlx)95Mo5 alloys

The temperature dependence of the electrical resistivity of (Cr_1−xAl_x)₉₅Mo₅ alloys with x = 0.11, 0.44, 0.77, 1.49, 2.07, 3.11, 4.84, 7.31 and 10.63%, was measured. The non-magnetic behaviour of the antiferromagnetic alloys (x = 0.11, 0.44, 0.77, 1.49, 7.31 and 10.63%) was determined by using the temperature dependence of the alloys with x = 2.07, 3.11 and 4.84% that remain paramagnetic at all temperatures, as a model. This allowed an analysis of the data in terms of existing theories.     

Electrical properties of (PBS)0·59TiS2 crystals at high pressures up to 20GPa

Abstract

The measurements of thermoelectric power S and resistance p at high pressure synthetic diamond anvils cell were performed for (PbS)0·59TiS2 and TiS2 crystals. The phase transition was found at P?;2GPa accompanied by descend of ρ and |S| for (PbS)o·59TiS2. This transition is connected with structural change of PbS fragment from pseudocubic cell to orthorombic one and as consequence, with change of the electron concentration in Tis2-layers. From the electronic structure calculations for TiS2, the semiconductor-metal transition occurs at pressure P ≥ 4 GPa. Experimentally at this pressure range the decrease of ρ(P) was observed for (PbS)0·59TiS2 crystals.     

Ultrahigh pressure equation of state of tantalum to 310 GPa

ABSTRACT

The isothermal compression of transition metal tantalum (Ta) was studied in a diamond anvil cell by X-ray diffraction utilizing rhenium (Re) and gold (Au) as internal X-ray pressure standards. The Re pressure marker was employed during non-hydrostatic compression to pressures up to 310?GPa while the Au pressure marker was used during quasi-hydrostatic compression in a neon pressure-transmitting medium to 80?GPa. Two ultra-high pressure experiments were conducted on Ta and Re mixtures utilizing focused-ion beam machined toroidal diamond anvils with central flats varying from 8 microns to 16 microns in diameter. The Ta metal was observed to be stable in the body-centered-cubic phase to a volume compression V/V₀?=?0.581. The measured equations of state (EOS) of Ta using two different calibrations of the Re pressure marker are compared with the ambient temperature isotherm derived from shock compression data. We provide a detailed analysis of EOS fit parameters for Ta under quasi-hydrostatic and non-hydrostatic conditions.     

The equation of state of triolein up to 1 GPa

In this paper, the compressibility studies of triolein up to 1 GPa at temperature range from 10°C to 50°C have been presented. The discontinuity of V(p) relation, characteristic for the first-order phase transition was observed. At higher temperatures (40°C and above), the time necessary for the phase transition rises considerably. Also the pressure–volume hysteresis due to the phase formation–decomposition cycle was enlarged.     

Static compression of rare earth metal holmium to 282 GPa

ABSTRACT

The phase transitions and equation of state measurements were carried out on rare earth metal Holmium (Ho) to 282?GPa using toroidal diamond anvils thereby doubling the pressure range to which it has been studied previously. The first set of experiment employed standard beveled diamond anvils utilizing copper as an x-ray pressure standard to 217?GPa. The second set of experiment employed toroidal diamond anvils utilizing platinum as an x-ray pressure standard to 282?GPa. The recently proposed 16-atom orthorhombic structure (oF16) appeared to be stable between 103 and 282?GPa. The scaled axial ratio (c/a) shows a narrow range of variation of 1.58?±?0.05 for the five known crystalline phases of Ho to 282?GPa. The experimental equation of state of Ho is presented up to a threefold volume compression V/V_o?=?0.322.