By using the chemical bond theory of dielectric description, the chemical bond parameters of (Tl, Pb) - 1223 was calculated. The results show that the Sr-O, Tl-O, and Ca-O types of bond have higher ionic character an...By using the chemical bond theory of dielectric description, the chemical bond parameters of (Tl, Pb) - 1223 was calculated. The results show that the Sr-O, Tl-O, and Ca-O types of bond have higher ionic character and the Cu-O types of bond have more covalent character. Mssbauer isomer shifts of 57Fe and 119Sn doped in (Tl, Pb) -1223 were calculated by using the chemical environmental factor, he, defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57Fe, and 119Sn doped (Tl, Pb) -1223 superconductor. We conclude that all of the Fe atoms substitute the Cu at square planar Cu (1) site, whereas Sn prefers to substitute the square pyramidal Cu (2) site.展开更多
By using the chemical bond theory of dielectric description, the chemical bond parameters of (Hg, Pb) 1223 were calculated. The results show that the (Ba, Sr) O and Ca-O types of bond have higher ionic character, wh...By using the chemical bond theory of dielectric description, the chemical bond parameters of (Hg, Pb) 1223 were calculated. The results show that the (Ba, Sr) O and Ca-O types of bond have higher ionic character, while the Cu-O and (Hg, Pb) O types of bond have more covalent character. Mssbauer isomer shifts of 57 Fe and 119 Sn doped in (Hg, Pb) 1223 were calculated by using the chemical environmental factor, h e, defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57 Fe and 119 Sn doped (Hg, Pb) 1223 superconductor. It can be concluded that all of the Fe atoms substitute the Cu at square planar Cu(1) site, whereas Sn prefers to substitute the square pyramidal Cu(2) site.展开更多
The mixed spinel ferrite system Mg0.95Mn0.05Fe2-2xTizxO4 （0 ≤x ≤ 0.7） was synthesized by the conventional solid-state reaction technique. The effect of Ti^4＋ doping was studied by using the Moessbauer spectroscop...The mixed spinel ferrite system Mg0.95Mn0.05Fe2-2xTizxO4 （0 ≤x ≤ 0.7） was synthesized by the conventional solid-state reaction technique. The effect of Ti^4＋ doping was studied by using the Moessbauer spectroscopy measurements at room temperature. From the analysis of the Moessbauer spectra, it is observed that s-electron density, electric field gradient （EFG）, quadrupole coupling constant （QCC） and the net hyperfine magnetic fields acting on the Moessbauer nuclei-FeA^3＋ and FeB^3＋ change with the increase of Ti^4＋ doping in Mg0.95Mn0.05Fe2O4. The hyperfine magnetic field decreases with the increase of Ti^4＋ doping.展开更多
The effect of non-magnetic Al^3＋ ion doping on the magnetic properties of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） spinel ferrites was studied using Moessbauer spectroscopy measurements at room temperature. From the Moessbaue...The effect of non-magnetic Al^3＋ ion doping on the magnetic properties of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） spinel ferrites was studied using Moessbauer spectroscopy measurements at room temperature. From the Moessbauer study, it is observed that the ：esolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel ferrites. The value of the isomer shift obtained from the fitting of the Moessbauer spectra indicates that Fe ions are in ＋3 state. A paramagnetic doublet is observed at ：iegree of inversion x=0.4, superimposed on the hyperfine sextets, indicating that the super-exchange interaction A-B decreases due to ：he dilution of sublattice by Al^3＋ ions. The hyperfine magnetic field decreases at both interstitial sites of tetrahedral （A） and 3ctahedral （B） with the increase in Al concentration.展开更多
The ^(229)Th isotope is a promising candidate for nuclear clocks.However,the clock transition varies due to the electron-induced nuclear frequency shift.To achieve the accuracy required for developing a nuclear clock,...The ^(229)Th isotope is a promising candidate for nuclear clocks.However,the clock transition varies due to the electron-induced nuclear frequency shift.To achieve the accuracy required for developing a nuclear clock,this effect must be precisely determined.In this work,we employed a non-perturbative multi-configuration Dirac-Hartree-Fock(MCDHF) method,in contrast to the perturbation theory used previously,to resolve the electron-induced field shift effect.As a more internally consistent ab initio method,this calculation accounts for subtle differences in the nuclear potential while considering the ^(229)Th isotope in both its ground and isomeric states.Consequently,the nuclear clock transition frequency difference between ^(229)Th^(3+)and ^(229)Th^(4+)was determined to be-639 MHz with computational convergency down to 1 MHz.Given recently measured transition frequency of ^(229)Th^(4+)in ^(229)Th-doped CaF_(2) [Nature 633,63(2024)],here the transition frequency of isolated ^(229)Th^(3+)is predicted to be 2020407009(1)comp.(77)_(δ/(r^(2)))(70)_(ext).MHz,with brackets indicating uncertainties stemming from our atomic structure computations,the nuclear charge radius difference from the literature,and the influence of the crystal environment as reported in the literature.This provides valuable guidance for direct laser excitation of isolated ^(229)Th^(3+)based on ion trap experiments.展开更多
文摘By using the chemical bond theory of dielectric description, the chemical bond parameters of (Tl, Pb) - 1223 was calculated. The results show that the Sr-O, Tl-O, and Ca-O types of bond have higher ionic character and the Cu-O types of bond have more covalent character. Mssbauer isomer shifts of 57Fe and 119Sn doped in (Tl, Pb) -1223 were calculated by using the chemical environmental factor, he, defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57Fe, and 119Sn doped (Tl, Pb) -1223 superconductor. We conclude that all of the Fe atoms substitute the Cu at square planar Cu (1) site, whereas Sn prefers to substitute the square pyramidal Cu (2) site.
基金ProjectsupportedbytheNationalNaturalScienceFoundationofChina (No .2 98710 2 9)
文摘By using the chemical bond theory of dielectric description, the chemical bond parameters of (Hg, Pb) 1223 were calculated. The results show that the (Ba, Sr) O and Ca-O types of bond have higher ionic character, while the Cu-O and (Hg, Pb) O types of bond have more covalent character. Mssbauer isomer shifts of 57 Fe and 119 Sn doped in (Hg, Pb) 1223 were calculated by using the chemical environmental factor, h e, defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57 Fe and 119 Sn doped (Hg, Pb) 1223 superconductor. It can be concluded that all of the Fe atoms substitute the Cu at square planar Cu(1) site, whereas Sn prefers to substitute the square pyramidal Cu(2) site.
基金Project supported by the Second Stage of Brain Korea 21 ProjectProject(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE),Korea
文摘The mixed spinel ferrite system Mg0.95Mn0.05Fe2-2xTizxO4 （0 ≤x ≤ 0.7） was synthesized by the conventional solid-state reaction technique. The effect of Ti^4＋ doping was studied by using the Moessbauer spectroscopy measurements at room temperature. From the analysis of the Moessbauer spectra, it is observed that s-electron density, electric field gradient （EFG）, quadrupole coupling constant （QCC） and the net hyperfine magnetic fields acting on the Moessbauer nuclei-FeA^3＋ and FeB^3＋ change with the increase of Ti^4＋ doping in Mg0.95Mn0.05Fe2O4. The hyperfine magnetic field decreases with the increase of Ti^4＋ doping.
基金Project supported by the Second Stage of Brain Korea 21 ProjectProject(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE),Korea
文摘The effect of non-magnetic Al^3＋ ion doping on the magnetic properties of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） spinel ferrites was studied using Moessbauer spectroscopy measurements at room temperature. From the Moessbauer study, it is observed that the ：esolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel ferrites. The value of the isomer shift obtained from the fitting of the Moessbauer spectra indicates that Fe ions are in ＋3 state. A paramagnetic doublet is observed at ：iegree of inversion x=0.4, superimposed on the hyperfine sextets, indicating that the super-exchange interaction A-B decreases due to ：he dilution of sublattice by Al^3＋ ions. The hyperfine magnetic field decreases at both interstitial sites of tetrahedral （A） and 3ctahedral （B） with the increase in Al concentration.
基金the support by the National Key Research and Development Program of China (Grant Nos. 2022YFA1602303, and 2022YFA1602500)the support by the National Key Research and Development Program of China (Grant Nos. 2023YFA1606501, and 2022YFA1602504)+5 种基金the support by the National Key Research and Development Program of China (Grant No. 2024YFA1610900)the National Natural Science Foundation of China (Grant Nos. 12074081, and 12104095)the National Natural Science Foundation of China (Grant Nos. 12474251, and 12204110)the National Natural Science Foundation of China (Grant No. 12447106)the support by the National Natural Science Foundation of China (Grant No. 12147101)the Guangdong Major Project of Basic and Applied Basic Research (Grant No. 2020B0301030008)。
文摘The ^(229)Th isotope is a promising candidate for nuclear clocks.However,the clock transition varies due to the electron-induced nuclear frequency shift.To achieve the accuracy required for developing a nuclear clock,this effect must be precisely determined.In this work,we employed a non-perturbative multi-configuration Dirac-Hartree-Fock(MCDHF) method,in contrast to the perturbation theory used previously,to resolve the electron-induced field shift effect.As a more internally consistent ab initio method,this calculation accounts for subtle differences in the nuclear potential while considering the ^(229)Th isotope in both its ground and isomeric states.Consequently,the nuclear clock transition frequency difference between ^(229)Th^(3+)and ^(229)Th^(4+)was determined to be-639 MHz with computational convergency down to 1 MHz.Given recently measured transition frequency of ^(229)Th^(4+)in ^(229)Th-doped CaF_(2) [Nature 633,63(2024)],here the transition frequency of isolated ^(229)Th^(3+)is predicted to be 2020407009(1)comp.(77)_(δ/(r^(2)))(70)_(ext).MHz,with brackets indicating uncertainties stemming from our atomic structure computations,the nuclear charge radius difference from the literature,and the influence of the crystal environment as reported in the literature.This provides valuable guidance for direct laser excitation of isolated ^(229)Th^(3+)based on ion trap experiments.
