Experimental research on high pressure phase transitions of Mo and Ta

Cai, Ling-Cang; Zeng, Zhao-Yi; Zhang, X.-L.; Hu, Jianbo

doi:10.1051/epjconf/20101000028

Cited by 5 publications

(3 citation statements)

References 15 publications

(21 reference statements)

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“…Temperatures were measured with threewavelength pyrometry. 20 They reported a steep increase in the melting temperature from 3450 K to 3770 K. For Mo, shock velocity measurements [21][22][23] and numerous theoretical calculations [24][25][26][27][28][29][30] are in stark disagreement with the DAC results. 1,31 One study 28 suggests that the reported DAC melting curve of Mo is a solid-solid transition from bcc to fcc, but so far no such transformations have been found from x-ray diffraction measurements in DAC.…”

Section: Introductionmentioning

confidence: 96%

Flash heating in the diamond cell: Melting curve of rhenium

Yang

Karandikar

Boehler

2012

Review of Scientific Instruments

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We have developed a multi-wavelength Fast Temperature Readout (FasTeR) spectrometer to capture a sample's transient temperature fluctuations, and reduce uncertainties in melting temperature determination. Without sacrificing accuracy, FasTeR features a fast readout rate (about 100 Hz), high sensitivity, large dynamic range, and a well-constrained focus. Complimenting a charge-coupled device spectrometer, FasTeR consists of an array of photomultiplier tubes and optical dichroic filters. The temperatures determined by FasTeR outside of the vicinity of melting are, generally, in good agreement with results from the charge-coupled device spectrometer. Near melting, FasTeR is capable of capturing transient temperature fluctuations, at least on the order of 300 K/s. A software tool, SIMFaster, is described and has been developed to simulate FasTeR and assess design configurations. FasTeR is especially suitable for temperature determinations that utilize ultra-fast techniques under extreme conditions. Working in parallel with the laser-heated diamond-anvil cell, synchrotron Mössbauer spectroscopy, and X-ray diffraction, we have applied the FasTeR spectrometer to measure the melting temperature of 57 Fe 0.9 Ni 0.1 at high pressure. C 2015 AIP Publishing LLC. [http://dx.

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Section: Introductionmentioning

confidence: 96%

Flash heating in the diamond cell: Melting curve of rhenium

Yang

Karandikar

Boehler

2012

Review of Scientific Instruments

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“…There is presently no experimental evidence for a solid-solid (s-s) transition in Mo. However, there is compelling theoretical evidence for a s-s phase transition at high pressures [12][13][14][15][16]. Our calculations of the phonon spectrum of bcc-Mo presented below (see Figure 1) clearly show its dynamic instability at 1000 GPa and low T, and previous simulations indicated that bcc-Mo dynamically destabilizes at ∼700 GPa [17,18].…”

Section: Molybdenum: An Example Of a Multi-phase Materialsmentioning

confidence: 55%

Generalization of the Unified Analytic Melt-Shear Model to Multi-Phase Materials: Molybdenum as an Example

et al. 2019

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The unified analytic melt-shear model that we introduced a decade ago is generalized to multi-phase materials. A new scheme for calculating the values of the model parameters for both the cold ( T = 0 ) shear modulus ( G ) and the melting temperature at all densities ( ρ ) is developed. The generalized melt-shear model is applied to molybdenum, a multi-phase material with a body-centered cubic (bcc) structure at low ρ which loses its dynamical stability with increasing pressure (P) and is therefore replaced by another (dynamically stable) solid structure at high ρ . One of the candidates for the high- ρ structure of Mo is face-centered cubic (fcc). The model is compared to (i) our ab initio results on the cold shear modulus of both bcc-Mo and fcc-Mo as a function of ρ , and (ii) the available theoretical results on the melting of bcc-Mo and our own quantum molecular dynamics (QMD) simulations of one melting point of fcc-Mo. Our generalized model of G ( ρ , T ) is used to calculate the shear modulus of bcc-Mo along its principal Hugoniot. It predicts that G of bcc-Mo increases with P up to ∼240 GPa and then decreases at higher P. This behavior is intrinsic to bcc-Mo and does not require the introduction of another solid phase such as Phase II suggested by Errandonea et al. Generalized melt-shear models for Ta and W also predict an increase in G followed by a decrease along the principal Hugoniot, hence this behavior may be typical for transition metals with ambient bcc structure that dynamically destabilize at high P. Thus, we concur with the conclusion reached in several recent papers (Nguyen et al., Zhang et al., Wang et al.) that no solid-solid phase transition can be definitively inferred on the basis of sound velocity data from shock experiments on Mo. Finally, our QMD simulations support the validity of the phase diagram of Mo suggested by Zeng et al.

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“…1 and 2. For Ta, the recent work of Cai et al [27] found a discontinuity of the longitudinal sound velocity against shock pressure at ∼60 GPa, which was identified as a possible structural phase transition for Ta. However, due to a lack of other experimental and theoretical data, it has not been included in the present calculation of Ta.…”

Section: -2mentioning

confidence: 96%

Multiphase Equation of States of the Solid and Liquid Phases of Al and Ta

Li¹,

Jing-Zhen²,

Li³

et al. 2012

Chinese Phys. Lett.

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The multiphase equation of states (EOSs) of both the solid and liquid phases of Al and Ta are presented. These EOSs are carried out on the basis of the Helmholtz free energy, where the ion vibration free energy is evaluated from the mean field potential (MFP) model we recently proposed [Physica B 406 (2011) 4163]. The calculated results show that our multiphase EOSs can give a good reproduction of the measured phase diagrams and other experimental data, including static high-pressure measurements, shock Hugoniots and the thermodynamic quantities of these metals.

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Experimental research on high pressure phase transitions of Mo and Ta

Cited by 5 publications

References 15 publications

Flash heating in the diamond cell: Melting curve of rhenium

Flash heating in the diamond cell: Melting curve of rhenium

Generalization of the Unified Analytic Melt-Shear Model to Multi-Phase Materials: Molybdenum as an Example

Multiphase Equation of States of the Solid and Liquid Phases of Al and Ta

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