High-pressure structures and metallization of sodium chloride

Chen, Xin; Ma, Yanming

doi:10.1209/0295-5075/100/26005

Cited by 18 publications

(12 citation statements)

References 38 publications

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“…To understand the underlying mechanism responsible for the above abnormal behavior, we conducted density-function-theory (DFT) based molecular dynamics simulations and electronic structure calculations. In order to clearly distinguish the difference in electronic structures between the initial state and the compressed one, we extended the high pressure to 78 GPa, considering the fact that the simulated pressure is often exploited to be much larger than the experimental ones in previous studies [31,32]. As shown in Fig.…”

Section: B Total Density Of States (Dos) and The Projected Dosmentioning

confidence: 99%

Polyamorphic transition in a transition metal based metallic glass under high pressure

Liu

Zeng

et al. 2019

Phys. Rev. B

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Pressure-induced glass-glass transition (GGT) has been reported in a few rare-earth based and main-group metallic glasses (MGs), and during which, the compressibility decreases with the transformation from a low-density to a high-density amorphous state. Herein, we report an unexpected GGT behavior in Pd-based MGs under pressure, which is characterized by an anomalous increase in the compressibility with the pressure. State-of-the-art high-energy synchrotron technique, coupled with theoretical simulations, reveals that this unique GGT behavior is primarily caused by the change in bonding characteristics, i.e., some covalent-like atomic bonds in the as-prepared state change to metallic ones under high pressure, which also leads to the increase in the compressibility. Our current findings shed new light on understanding the nature of polyamorphic transitions in MGs.

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Section: B Total Density Of States (Dos) and The Projected Dosmentioning

confidence: 99%

Polyamorphic transition in a transition metal based metallic glass under high pressure

Liu

Zeng

et al. 2019

Phys. Rev. B

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“…The hydrostatic transformation pressure has been amply theoretically calculated (Lu et al ., ). The higher transition from the CsCl‐type structure of NaCl to the layered CrB‐type structure (space group Cmcm ) of sodium chloride would occur from 322 GPa hydrostatic pressures on (Chen and Ma, ). This polymorph would become metallic when pressed to above 584 GPa (Chen and Ma, ).…”

Section: Physical Backgroundmentioning

confidence: 99%

“…The higher transition from the CsCl‐type structure of NaCl to the layered CrB‐type structure (space group Cmcm ) of sodium chloride would occur from 322 GPa hydrostatic pressures on (Chen and Ma, ). This polymorph would become metallic when pressed to above 584 GPa (Chen and Ma, ). But such pressures are hardly reached with hydrostatic equipment.…”

Section: Physical Backgroundmentioning

confidence: 99%

“…The penetrations are far away from the “effective” h cone value for the “effective tip radius.” Importantly, the straight second branch of the soda‐lime‐glass analysis of another loading curve from the same paper up to 30 µm depth secures the NaCl kink (21.1 µm) from concern about any tip irregularity at that depth being the reason for the kink. The very high load in the macroindentation region might thus be suspicious for the secondary transformation of NaCl from the CsCl‐ to the CrB‐structure (Chen and Ma, ). But repetition of the macroindentation is urgently required with proper instrumentation.…”

Section: Physical Backgroundmentioning

confidence: 99%

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Activation energy of the low-load NaCl transition from nanoindentation loading curves

Kaupp

2014

Scanning

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Access to activation energies E(a) of phase transitions is opened by unprecedented analyses of temperature dependent nanoindentation loading curves. It is based on kinks in linearized loading curves, with additional support by coincidence of kink and electrical conductivity of silicon loading curves. Physical properties of B1, B2, NaCl and further phases are discussed. The normalized low-load transition energy of NaCl (Wtrans/µN) increases with temperature and slightly decreases with load. Its semi-logarithmic plot versus T obtains activation energy E(a)/µN for calculation of the transition work for all interesting temperatures and pressures. Arrhenius-type activation energy (kJ/mol) is unavailable for indentation phase transitions. The E(a) per load normalization proves insensitive to creep-on-load, which excludes normalization to depth or volume for large temperature ranges. Such phase transition E(a)/µN is unprecedented material's property and will be of practical importance for the compatibility of composite materials under impact and further shearing interactions at elevated temperatures.

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“…The preferred hydrostatic transition pressure is known as 26.8 GPa [9]. The calculated second phase transition (bcc to layered CrB-type NaCl space group Cmcm) is hydrostatically expected at 322 GPa, metallic from 584 GPa [10]. Most probably, the second transition corresponds with the kink in the Kaupp-plot at 2.49 N load and 21.1 µm depth [8] according to the loading curve of ref.…”

Section: Macroscopic Depth-sensing Hardness and Phase Transitionsmentioning

confidence: 90%

Challenge of Industrial High-load One-point Hardness and of Depth Sensing Modulus

Kaupp¹

2017

J Material Sci Eng

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The physics of industrial single-point force indentation hardness measurements (Vickers, Knoop, Brinell, Rockwell, Shore, Leeb, and others) is compared with the depth-sensing nano, micro, and macro instrumental hardness technique that provides several further mechanical parameters, when using the correct force/depth curves exponent 3/2 on the depth of the loading curves. Only the latter reveal phase change onset with transition energy, and temperaturedependent activation energy, which provides important information for applications of all types of solids, but is not considered in the ISO or ASTM standards. Furthermore, the high-load one-point techniques leave the inevitably even stronger and more diverse consecutive phase-transformations undetected, so that the properties of pristine materials are not obtained. But materials are mostly not (continuously) applied under so high load, which must lead to severe misinterpretations. The dilemma of ISO or ASTM standards violating the basic energy law, the dimensional law, and denying the occurrence of phase changes under load is demonstrated with the physics of depth-sensing indentations. Transformation of iterated ISO-hardness and finite element simulated hardness to physical hardness is exemplified. The one-point techniques remain important for industry, but they must be complemented by physical hardness with detection of the phase transformation onset sequences for the reliability of their results.The elastic modulus E ISO from unloading curves as hitherto unduly called "Young's" modulus has nothing in common with unidirectional Young's modulus according to Hook's law, because the skew tip faces collect contributions from all crystal faces including shear moduli, while iteration fit is to Young's modulus of a standard. Unphysical and also physically corrected multidirectional indentation moduli mixtures of mostly anisotropic materials and there from deduced mechanical parameters have no physical basis and none of these should be used any more. A possible solution of this dilemma might be the use of indentation-E phys and bulk moduli K from hydrostatic compression measurements. The reasons for obeying physical laws in the mechanics of materials are stressed.

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High-pressure structures and metallization of sodium chloride

Cited by 18 publications

References 38 publications

Polyamorphic transition in a transition metal based metallic glass under high pressure

Polyamorphic transition in a transition metal based metallic glass under high pressure

Activation energy of the low-load NaCl transition from nanoindentation loading curves

Challenge of Industrial High-load One-point Hardness and of Depth Sensing Modulus

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