Using a pseudopotential plane-waves method,we calculate the phonon dispersion curves,thermodynamic properties,and hardness values of α-CdP;and β-CdP;under high pressure.From the studies of the phonon property and en...Using a pseudopotential plane-waves method,we calculate the phonon dispersion curves,thermodynamic properties,and hardness values of α-CdP;and β-CdP;under high pressure.From the studies of the phonon property and enthalpy difference curves,we discuss a phase transform from β-CdP;to a-CdP;in a pressure range between 20 GPa and 25 GPa.Then,the thermodynamic properties,Debye temperatures,and heat capacities are investigated at high pressures.What is more,we employ a semiempirical method to evaluate the pressure effects on the hardness for these two crystals.The results show that the hardness values of both α-CdP;and β-CdP;increase as pressure is increased.The influence mechanism of the pressure effect on the hardness of CdP;is also briefly discussed.展开更多
Hydrous minerals play a critical role in modifying the physical and chemical properties of the Earth’s interior.Among those,epidote is an important hydrous mineral in greenschist and blueschist phases of the metamorp...Hydrous minerals play a critical role in modifying the physical and chemical properties of the Earth’s interior.Among those,epidote is an important hydrous mineral in greenschist and blueschist phases of the metamorphosed subducting crust at shallow depth(30-60 km).Here,we measured the compressional(P)and shear(S)wave velocities of a polycrystalline epidote sample at pressures up to 7 GPa and room temperature by means of ultrasonic interferometry.The obtained sound velocities and elastic moduli of epidote increase monotonically with pressure.Finite strain analysis on those data set yielded the elastic moduli and their pressure derivatives of epidote at ambient condition as follows:K_(S0)=115.2 GPa,G_(0)=66.7 GPa,K'_(s)=4.6,G'=1.1.Using the elastic properties of epidote,we set up a model to better understand the velocity jumps in the subducted oceanic crusts concerning the blueschist-eclogite transition at 60-90 km depths.Our results indicate that the calculated P and S wave velocity jumps are in good agreement with those seismic observations in the typical subduction zones such as northeastern Japan and southwestern Japan.The eclogitization from epidote bearing blueschist may provide an explanation for the wave velocity anomalies occurred in those regions.展开更多
In the era of miniaturization,the one-dimensional nanostructures presented numerous possibilities to realize operational nanosensors and devices by tuning their electrical transport properties.Upon size reduction,the ...In the era of miniaturization,the one-dimensional nanostructures presented numerous possibilities to realize operational nanosensors and devices by tuning their electrical transport properties.Upon size reduction,the physical properties of materials become extremely challenging to characterize and understand due to the complex interplay among structures,surface properties,strain effects,distribution of grains,and their internal coupling mechanism.In this report,we demonstrate the fabrication of a single metal-carbon composite nanowire inside a diamondanvil-cell and examine the in situ pressure-driven electrical transport properties.The nanowire manifests a rapid and reversible pressure dependence of the strong nonlinear electrical conductivity with significant zero-bias differential conduction revealing a quantum tunneling dominant carrier transport mechanism.We fully rationalize our observations on the basis of a metal-carbon framework in a highly compressed nanowire corroborating a quantum-tunneling boundary,in addition to a classical percolation boundary that exists beyond the percolation threshold.The structural phase progressions were monitored to evidence the pressure-induced shape reconstruction of the metallic grains and modification of their intergrain interactions for successful explanation of the electrical transport behavior.The pronounced sensitivity of electrical conductivity to an external pressure stimulus provides a rationale to design low-dimensional advanced pressure sensing devices.展开更多
In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation...In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.展开更多
Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic ex- citation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the el...Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic ex- citation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the electron temperature is increased, which means that the lattice of β-cristobalite becomes unstable under intense laser irradiation. In addition, for the optic phonon mode, the LO（H）-TO（H） splitting disappears when the electronic temperature reaches a certain value, corresponding to the whole transverse-acoustic phonon branches becoming negative. It means that the electronic excitation destroys the macroscopic electric field of β-cristobalite. Based on the calculated phonon band structures, some thermo- dynamic properties are calculated as a function of temperature at different electronic temperatures. These investigations provide evidence that non-thermal melting takes place during a femtosecond pulse laser interaction with β-cristobalite.展开更多
In situ pressure-induced Raman spectral changes of 1-octyl-3-methyl imidazolium hexafluorophosphate([OMIM][PF6])have been investigated under the pressure up to 5.86 GPa at room temperature.The results indicated that[O...In situ pressure-induced Raman spectral changes of 1-octyl-3-methyl imidazolium hexafluorophosphate([OMIM][PF6])have been investigated under the pressure up to 5.86 GPa at room temperature.The results indicated that[OMIM][PF6]experienced a phase transition at about4.12 GPa during compression,and it was thought as a phase transition of liquid to a superpressurized glass.Upon decompression,from the obvious change of Raman spectra of[OMIM][PF6]at about 0.48 GPa,it could be inferred that a decompression-induced disorder to order phase transition in[OMIM][PF6]occurred.The phase behavior of[OMIM][PF6]at low temperature under atmospheric pressure was also investigated in detail.The result showed that Raman spectra of[OMIM][PF6]varied slightly and no crystallization occurred upon cooling.These facts suggested that a disorder to order phase transition was induced by decompression in[OMIM][PF6],and[OMIM][PF6]served as a superpressurized glass under the pressure above4.12 GPa,which was similar to the glassy state at low temperature.展开更多
Dehydro-Diels-Alder(DDA)reaction is a textbook reaction for preparing six-membered rings in solution but is scarcely seen in solid-state synthesis.In this work,using multiple characterization techniques,we demonstrate...Dehydro-Diels-Alder(DDA)reaction is a textbook reaction for preparing six-membered rings in solution but is scarcely seen in solid-state synthesis.In this work,using multiple characterization techniques,we demonstrate that the bowl-shaped clusters C_(18)Te_(3)Br_(4)(Bu-O)_(6) might experience a DDA reaction at room temperature and high pressure between 5.5 and 7.4 GPa.Above 17.0 GPa,it is found that the bonding conversion from the intramolecular sp^(2) to the intermolecular spa occurred,in the form of pressure-induced diamondization.The recovered samples from 20.0 and 36.1 GPa showed incomplete reversibility,while the decompression-induced graphitization of glassy carbon was observed during decompression from 46.5 GPa.The electrochemical impedance spectroscopy results indicated that the transport properties changed from grain boundary dominant to grain dominant due to the DDA reaction and the grain boundary effect disappeared as the intermolecular sp3 bonding building-up and carrier transmission channel formation above 17.0 GPa.The results in this study open a new route to construct the crystalline carbon materials with different transport properties.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11547158)the Doctoral Fund of Zhengzhou University of Light Industry,China(Grant Nos.2014BSJJ088 and 2015XJJZ022)
文摘Using a pseudopotential plane-waves method,we calculate the phonon dispersion curves,thermodynamic properties,and hardness values of α-CdP;and β-CdP;under high pressure.From the studies of the phonon property and enthalpy difference curves,we discuss a phase transform from β-CdP;to a-CdP;in a pressure range between 20 GPa and 25 GPa.Then,the thermodynamic properties,Debye temperatures,and heat capacities are investigated at high pressures.What is more,we employ a semiempirical method to evaluate the pressure effects on the hardness for these two crystals.The results show that the hardness values of both α-CdP;and β-CdP;increase as pressure is increased.The influence mechanism of the pressure effect on the hardness of CdP;is also briefly discussed.
基金supported by the National Natural Science Foundation of China(NSFC)Major Research Plan on West-Pacific Earth System Multispheric Interactions(project number:91958216)NSFC(project number:42374211)the Fundamental Research Funds for the Central Universities.
文摘Hydrous minerals play a critical role in modifying the physical and chemical properties of the Earth’s interior.Among those,epidote is an important hydrous mineral in greenschist and blueschist phases of the metamorphosed subducting crust at shallow depth(30-60 km).Here,we measured the compressional(P)and shear(S)wave velocities of a polycrystalline epidote sample at pressures up to 7 GPa and room temperature by means of ultrasonic interferometry.The obtained sound velocities and elastic moduli of epidote increase monotonically with pressure.Finite strain analysis on those data set yielded the elastic moduli and their pressure derivatives of epidote at ambient condition as follows:K_(S0)=115.2 GPa,G_(0)=66.7 GPa,K'_(s)=4.6,G'=1.1.Using the elastic properties of epidote,we set up a model to better understand the velocity jumps in the subducted oceanic crusts concerning the blueschist-eclogite transition at 60-90 km depths.Our results indicate that the calculated P and S wave velocity jumps are in good agreement with those seismic observations in the typical subduction zones such as northeastern Japan and southwestern Japan.The eclogitization from epidote bearing blueschist may provide an explanation for the wave velocity anomalies occurred in those regions.
基金the National Natural Science Foundation of China (No.11874076)the National Science Associated Funding (NSAF)(No.U1530402)Science Challenging Program (No.TZ2016001).S.S.would also like to thank Dr.Christophe Thissieu from Almax easy Lab Inc, MA,Cambridge,USA for providing the designer diamond anvils for the experiments.S.S. would like to thank Du Ankita Ghatak,S.N.Bose National Centre for Basic Sciences,Kolkata,India for the analysis and discussion on HRTEM data.
文摘In the era of miniaturization,the one-dimensional nanostructures presented numerous possibilities to realize operational nanosensors and devices by tuning their electrical transport properties.Upon size reduction,the physical properties of materials become extremely challenging to characterize and understand due to the complex interplay among structures,surface properties,strain effects,distribution of grains,and their internal coupling mechanism.In this report,we demonstrate the fabrication of a single metal-carbon composite nanowire inside a diamondanvil-cell and examine the in situ pressure-driven electrical transport properties.The nanowire manifests a rapid and reversible pressure dependence of the strong nonlinear electrical conductivity with significant zero-bias differential conduction revealing a quantum tunneling dominant carrier transport mechanism.We fully rationalize our observations on the basis of a metal-carbon framework in a highly compressed nanowire corroborating a quantum-tunneling boundary,in addition to a classical percolation boundary that exists beyond the percolation threshold.The structural phase progressions were monitored to evidence the pressure-induced shape reconstruction of the metallic grains and modification of their intergrain interactions for successful explanation of the electrical transport behavior.The pronounced sensitivity of electrical conductivity to an external pressure stimulus provides a rationale to design low-dimensional advanced pressure sensing devices.
基金This work was supported by the "Outstanding Youth Fund" of the National Natural Science Foundation of China (Grant No. 59725105) the "Hundreds of Talents" Program of the Chinese Academy of Sciences.
文摘In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0-35 GPa. One was at about 1.3 GPa with the crystal structure changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic back to another tetragonal.
基金support by the National Natural Science Foundation of China(Grant Nos.11374217 and 11547158)
文摘Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic ex- citation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the electron temperature is increased, which means that the lattice of β-cristobalite becomes unstable under intense laser irradiation. In addition, for the optic phonon mode, the LO（H）-TO（H） splitting disappears when the electronic temperature reaches a certain value, corresponding to the whole transverse-acoustic phonon branches becoming negative. It means that the electronic excitation destroys the macroscopic electric field of β-cristobalite. Based on the calculated phonon band structures, some thermo- dynamic properties are calculated as a function of temperature at different electronic temperatures. These investigations provide evidence that non-thermal melting takes place during a femtosecond pulse laser interaction with β-cristobalite.
基金supported by the National Natural Science Foundation of China(21273206)the Natural Science Foundation of Henan Province(2010GGJS-110)
文摘In situ pressure-induced Raman spectral changes of 1-octyl-3-methyl imidazolium hexafluorophosphate([OMIM][PF6])have been investigated under the pressure up to 5.86 GPa at room temperature.The results indicated that[OMIM][PF6]experienced a phase transition at about4.12 GPa during compression,and it was thought as a phase transition of liquid to a superpressurized glass.Upon decompression,from the obvious change of Raman spectra of[OMIM][PF6]at about 0.48 GPa,it could be inferred that a decompression-induced disorder to order phase transition in[OMIM][PF6]occurred.The phase behavior of[OMIM][PF6]at low temperature under atmospheric pressure was also investigated in detail.The result showed that Raman spectra of[OMIM][PF6]varied slightly and no crystallization occurred upon cooling.These facts suggested that a disorder to order phase transition was induced by decompression in[OMIM][PF6],and[OMIM][PF6]served as a superpressurized glass under the pressure above4.12 GPa,which was similar to the glassy state at low temperature.
基金This work was supported by the National Natural Science Foundation of China(Nos.52090020 and 11874076)the National Research Foundation of Korea(Nos.2016K1A4A3914691 and 2018R1DA1B070498).
文摘Dehydro-Diels-Alder(DDA)reaction is a textbook reaction for preparing six-membered rings in solution but is scarcely seen in solid-state synthesis.In this work,using multiple characterization techniques,we demonstrate that the bowl-shaped clusters C_(18)Te_(3)Br_(4)(Bu-O)_(6) might experience a DDA reaction at room temperature and high pressure between 5.5 and 7.4 GPa.Above 17.0 GPa,it is found that the bonding conversion from the intramolecular sp^(2) to the intermolecular spa occurred,in the form of pressure-induced diamondization.The recovered samples from 20.0 and 36.1 GPa showed incomplete reversibility,while the decompression-induced graphitization of glassy carbon was observed during decompression from 46.5 GPa.The electrochemical impedance spectroscopy results indicated that the transport properties changed from grain boundary dominant to grain dominant due to the DDA reaction and the grain boundary effect disappeared as the intermolecular sp3 bonding building-up and carrier transmission channel formation above 17.0 GPa.The results in this study open a new route to construct the crystalline carbon materials with different transport properties.
