The high-frequency edge of the first-order Raman mode of diamond reflects the stress state at the culet of anvil, and is often used for the pressure calibration in diamond anvil cell(DAC) experiments. Here we point ou...The high-frequency edge of the first-order Raman mode of diamond reflects the stress state at the culet of anvil, and is often used for the pressure calibration in diamond anvil cell(DAC) experiments. Here we point out that the high-frequency edge of the diamond Raman phonon corresponds to the Brillouin zone(BZ) center Γ point as a function of pressure. The diamond Raman pressure gauge relies on the stability of crystal lattice of diamond under high stress. Upon the diamond anvil occurs failure under the uniaxial stress(197 GPa), the loss of intensity of the first-order Raman phonon and a stressdependent broad Raman band centered at 600 cm^(-1) are observed, which is associated with a strain-induced local mode corresponding to the BZ edge phonon of the L1 transverse acoustic phonon branch.展开更多
High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), whi...High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works,a further study indicates that the C_(44)/C_(44)ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.展开更多
A new extended solid nitrogen,referred to as post-layered-polymeric nitrogen(PLP-N,or Panda-N),was observed by further heating the layered-polymeric nitrogen(LP-N)to above 2300 K at 161 GPa.The new phase is found to b...A new extended solid nitrogen,referred to as post-layered-polymeric nitrogen(PLP-N,or Panda-N),was observed by further heating the layered-polymeric nitrogen(LP-N)to above 2300 K at 161 GPa.The new phase is found to be very optically transparent and exhibits ultra-large d-spacings ranging from 2.8 to 4.9 A at 172 GPa,suggesting a lower-symmetry large-unit-cell 2D chain-like or OD cluster-type structure with wide bandgap.However,the observed x-ray diffraction pattern and Raman scattering data cannot match any predicted structures in the published literature.This finding further complicates the phase diagram of nitrogen and also highlights the path dependence of the high-pressure dissociative transition in nitrogen.In addition,the phase transition from cubic gauche nitrogen(cg-N)to LP-N is observed at 157 GPa and 2000K.展开更多
We observed an isostructural phase transition in the solid nitrogen λ-N_(2) at approximately 50 GPa accompanied by anomalies in lattice parameters,atomic volume and Raman vibron modes.The anomalies are ascribed to a ...We observed an isostructural phase transition in the solid nitrogen λ-N_(2) at approximately 50 GPa accompanied by anomalies in lattice parameters,atomic volume and Raman vibron modes.The anomalies are ascribed to a slight reorientation of the nitrogen molecules,which does not seem to affect the monoclinic symmetry(space group P2_(1)/c).Our ab initio calculations further confirm the phenomena,and suggest an optimized structure for the λ-N_(2) phase.In addition,a new high-pressure amorphous phase of η′-N_(2) was also discovered by a detailed investigation of the pressure-temperature phase diagram of nitrogen with the aim of probing the phase stability of λ-N_(2).Our result may provide helpful information about the crystallographic nature of dissociation transitions in diatomic molecular crystals(H_(2),O_(2),N_(2),etc).展开更多
Thermoelectric technologies,which generate electricity directly from waste heat,have received considerable attention because of their potential to improve overall energy efficiency[1].The energy conversion efficiency ...Thermoelectric technologies,which generate electricity directly from waste heat,have received considerable attention because of their potential to improve overall energy efficiency[1].The energy conversion efficiency is evaluated by a dimensionless figure-of-merit,defined as ZT=α^(2)σT/κ,whereα,σ,T,andκare the Seebeck coefficient,electrical conductivity,absolute temperature,and thermal conductivity,respectively.展开更多
基金Project support by the National Natural Science Foundation of China(Grant No.11774247)。
文摘The high-frequency edge of the first-order Raman mode of diamond reflects the stress state at the culet of anvil, and is often used for the pressure calibration in diamond anvil cell(DAC) experiments. Here we point out that the high-frequency edge of the diamond Raman phonon corresponds to the Brillouin zone(BZ) center Γ point as a function of pressure. The diamond Raman pressure gauge relies on the stability of crystal lattice of diamond under high stress. Upon the diamond anvil occurs failure under the uniaxial stress(197 GPa), the loss of intensity of the first-order Raman phonon and a stressdependent broad Raman band centered at 600 cm^(-1) are observed, which is associated with a strain-induced local mode corresponding to the BZ edge phonon of the L1 transverse acoustic phonon branch.
基金financially supported by the National Natural Science Foundation of China (Grant Nos. 11774247 and U2030107)Sichuan University Innovation Research Program of China (Grant No. 2020SCUNL107)。
文摘High-pressure Raman scattering from hexagonal close-packed(HCP) metals Os and Re have been extended up to 200 GPa, and the pressure-dependent shear modulus C_(44)has been deduced from the Raman-active mode E_(28), which is generated from the adjacent vibration of atoms in hexagonal planes, providing the valuable information about the elastic properties for HCP metals under high pressure. Combined with the available data of HCP metals from previous works,a further study indicates that the C_(44)/C_(44)ratio would be close to a constant value, 0.01, with increasing atomic number of metals. The results obtained from high-pressure Raman scattering will allow us to probe the elastic anisotropy of the HCP metals at very high pressure.
基金Supported by the National Natural Science Foundation of China(Grant No.11774247)the Chinese Academy of Sciences(Grant No.2019-SSRF-PT-009588)。
文摘A new extended solid nitrogen,referred to as post-layered-polymeric nitrogen(PLP-N,or Panda-N),was observed by further heating the layered-polymeric nitrogen(LP-N)to above 2300 K at 161 GPa.The new phase is found to be very optically transparent and exhibits ultra-large d-spacings ranging from 2.8 to 4.9 A at 172 GPa,suggesting a lower-symmetry large-unit-cell 2D chain-like or OD cluster-type structure with wide bandgap.However,the observed x-ray diffraction pattern and Raman scattering data cannot match any predicted structures in the published literature.This finding further complicates the phase diagram of nitrogen and also highlights the path dependence of the high-pressure dissociative transition in nitrogen.In addition,the phase transition from cubic gauche nitrogen(cg-N)to LP-N is observed at 157 GPa and 2000K.
基金supported by the Sichuan University Innovation Research Program of China(Grant No.2020SCUNL107)the National Natural Science Foundation of China(Grant No.U2030107,11774247,and 11974154)+1 种基金Chinese Academy of Sciences(Grant Nos.2019-BEPC-PT003237 and 2020-SSRF-PT-012109)the Natural Science Foundation of Shandong Province(Grant Nos.2019GGX103023 and Z2018S008)。
文摘We observed an isostructural phase transition in the solid nitrogen λ-N_(2) at approximately 50 GPa accompanied by anomalies in lattice parameters,atomic volume and Raman vibron modes.The anomalies are ascribed to a slight reorientation of the nitrogen molecules,which does not seem to affect the monoclinic symmetry(space group P2_(1)/c).Our ab initio calculations further confirm the phenomena,and suggest an optimized structure for the λ-N_(2) phase.In addition,a new high-pressure amorphous phase of η′-N_(2) was also discovered by a detailed investigation of the pressure-temperature phase diagram of nitrogen with the aim of probing the phase stability of λ-N_(2).Our result may provide helpful information about the crystallographic nature of dissociation transitions in diatomic molecular crystals(H_(2),O_(2),N_(2),etc).
基金the financial support of the National Natural Science Foundation of China(52222209,11934007,and 52002167)the Science and Technology Innovation Committee Foundation of Shenzhen(JCYJ20220530165000001 and JCYJ20200109141205978)+2 种基金the Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)the Outstanding Talents Training Fund in Shenzhen(202108)the Natural Science Foundation of Sichuan(2023NSFSC0953)。
文摘Thermoelectric technologies,which generate electricity directly from waste heat,have received considerable attention because of their potential to improve overall energy efficiency[1].The energy conversion efficiency is evaluated by a dimensionless figure-of-merit,defined as ZT=α^(2)σT/κ,whereα,σ,T,andκare the Seebeck coefficient,electrical conductivity,absolute temperature,and thermal conductivity,respectively.
