Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a ...Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a temperature between 1100℃and 1200℃.The structure ofα-MoP_(2) and its relationship to other transition metal diphosphides are discussed.Surprisingly,the ambient pressure phase orthorhombicβ-MoP_(2)(space group Cmc21)is denser in structure thanα-MoP_(2).Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition fromβ-MoP_(2) to α-MoP_(2),suggesting thatα-MoP_(2) is a stable phase at ambient conditions;this is also supported by the total energy and phonon calculations.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
基金Project supported by the National Natural Science Foundation of China (Grant Nos.92065201,11874264,and 11974154)the Starting Grant of ShanghaiTech University and Analytical Instrumentation Center,SPST,ShanghaiTech University (Grant No.SPST-AIC10112914)support from the Natural Science Foundation of Shandong Province,China (Grant No.ZR2022MA004)。
文摘Monoclinicα-MoP_(2),with the OsGe2-type structure(space group C2/m,Z=4)and lattice parameters a=8.7248(11)Å,b=3.2322(4)Å,c=7.4724(9)Å,andβ=119.263°,was synthesized under a pressure of 4~GPa at a temperature between 1100℃and 1200℃.The structure ofα-MoP_(2) and its relationship to other transition metal diphosphides are discussed.Surprisingly,the ambient pressure phase orthorhombicβ-MoP_(2)(space group Cmc21)is denser in structure thanα-MoP_(2).Room-temperature high-pressure x-ray diffraction studies exclude the possibility of phase transition fromβ-MoP_(2) to α-MoP_(2),suggesting thatα-MoP_(2) is a stable phase at ambient conditions;this is also supported by the total energy and phonon calculations.
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).
