A first-principles study of B2 NiAl alloyed with rare earth element Pr, Pm, Sm, and Eu

The structural, elastic, and electronic properties of NiAl alloyed with rare earth elements Pr, Pm, Sm, and Eu are investigated by using density functional theory (DFT). The study suggests that Pr, Pm, Sm, and Eu are all tend to be substituted for Al site. Ni₈Al₇Pm possesses the largest ductility. Only the hardness and ductility of Ni₈Al₇Eu are enhanced simultaneously. The covalency strength of Ni-Al bond in Ni₈Al₇Pm is higher than that in Ni₈Al₇Eu. The covalency strength of Al-Al bond and that of Ni-Ni bond in Ni₈Al₇Eu are higher than that in Ni₈Al₇Pm. Ni-Pm bond and Ni-Eu bond are covalent, and the covalency strength of Ni-Pm bond is greater. Al-Pm bond and Al-Eu bond show great covalency strength and ionicity, respectively.     

Spin and orbital magnetic moments and spin anisotropy energies of light rare earth atoms embedded in graphene: A first-principles study

The geometries, electronic structures, spin magnetic moments (SMMs), orbital magnetic moments (OMMs) and spin anisotropy energies (SAEs) of light rare earth atoms (La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd) embedded in graphene were studied by using first-principles calculations based on Density Functional Theory (DFT). The spin-orbital coupling effect was taken into account and GGA+U method was adopted to describe the strongly localized and correlated 4f electrons. There is a significant deformation of the graphene plane after doping and optimization. The deformation of Gd doped graphene is the largest, while Eu the smallest. The results show that the valence is +3 for La, Ce, Pr, Nd, Pm, Sm and Gd, and +2 for Eu. Except Eu and Gd, there are obvious OMMs. When the spin is in the Z direction, the OMMs are −0.941 μ_B, −1.663 μ_B, −3.239 μ_B, −3.276 μ_B and −3.337 μ_B for Ce, Pr, Nd, Pm and Sm, respectively, and point the opposite direction of SMMs. All the doped systems except Gd show considerable SAEs. For Ce, Pr, Nd, Pm, Sm, and Eu, the SAEs are −0.928 meV, 20.941 meV, −8.848 meV, 7.855 meV, 75.070 meV and 0.810 meV, respectively. When the spin orientation is different, different orbital angular moments lead to apparent charge density difference of the 4f atoms, which can also explain the origin of SAEs.     

Exploring new mass regions with the ISOLTRAP spectrometer

First direct mass measurements on rare earth isotopes around ¹⁴⁶Gd have been performed with the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. More than 40 isotopes of the elements Pr, Nd, Pm, Sm, Eu, Dy and Ho have been measured with an accuracy of typically 1 × 10^-7. In the case of ¹⁴¹Sm isomeric and ground state (ΔE = 175 keV) were resolved. Since isobaric contaminations are present in the ISOLDE beam, these measurements on rare earth isotopes became only possible after the installation of a new cooler trap which acts an isobar separator. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of the structural stability of LnNbxOy systems (Ln = La, Ce, Pr, Nd, Pm, Sm, Eu) by the Xα method of discrete variation

The electronic structure and Ln-O (Ln = La, Ce, Pr, Nd, Pm, Sm, Eu) bonding parameters have been calculated by the X _α method of discrete variation taking into account the real structure of LaNb₇O₁₂ oxoniobate. It is shown that the experimentally observed tendencies in the change in the oxoniobate stability correlate with the decrease in the average electron-proton binding energy of LnO₈ clusters and enhanced repulsion between Ln and O orbitals to the end of the lanthanide series. Original Russian Text ? E.I. Yurieva, O.G. Reznitskikh, V.G. Bamburov, 2009, published in Izvestiya Rossiiskoi Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 7, pp. 1066–1068.     

On-line nuclear orientation of the deformed neutron-deficient Eu,Sm and Pm isotopes

Low-temperature nuclear orientation measurements made on-line at the SERC Daresbury Laboratory on^142m Eu,^141m Sm, and¹⁴¹Pm, with known magnetic dipole moments, have yielded the magnitude of the hyperfine fields of these isotopes in an iron host lattice. Thus measurements for the isotopes^{139, 138}Eu,^139m Sm, and¹³⁸Pm yielded values for the respective magnetic moments. Limits on the thermal relaxation times of Eu and Sm isotopes in Fe were also deduced. The results for¹³⁸Eu appear to contradict the earlier πh_11/2⊗νh_11/2 ground-state configuration assignment.     

Quantum-chemical features of Ln—O interatomic interactions in LnNbxOy (Ln=La, Ce, Pr, Nd, Pm, Sm, Eu) systems

Properties of the lanthanide—oxygen bonds in lanthanide niobates LnNb₇O₁₂(Ln=La, Ce, Pr, Nd, Pm, Sm, Eu) have been studied using the ab initio cluster X _α discrete variational method with two different basis sets of molecular orbitals. It has been found that the structural instability of lanthanides LnNb₇O₁₂ (Ln=Nd, Sm) observed in experiments is due to the combined effect of decrease in the stability of [LnO₈] cluster and increase in quantum-mechanical Ln—O repulsion when the minimum near neodymium (in the first model of the basis set of molecular orbitals) or praseodymium (in the second model of the basis set of molecular orbitals) atoms is passed.     

The (nth, α) reaction on 147Sm, 151, 153Eu and Yb isotopes

The (n, α) reaction has been studied using the highly pure thermal neutron beam from the 87m curved neutron guide at the Grenoble high flux reactor. The ¹⁴⁷Sm(n, α)¹⁴⁴Nd reaction showed up five lines corresponding to the ground and the first four excited states of the final nucleus. It is shown that ≈53 % of the 581 μb (n, α) cross section comes from the neutron capture by a bound level of the ¹⁴⁸Sm compound nucleus. The 8.7 ± 3 μb cross section of ¹⁵¹Eu(n, α)¹⁴⁸Pm seems to consist principally of at least two lines corresponding to the ground and the second excited states of ¹⁴⁸Pm. The ¹⁵³Eu(n, α)¹⁴⁹Pm cross section for thermal neutrons is ≦ 1 μb. The lower limits of (n, α) thermal neutron cross section values on ytterbium isotopes are ≈ 20 to 40 times lower than the published data.     

电子俘获材料Eu,Sm∶CaS荧光特性的研究

研究了电子俘获材料Eu ,Sm∶CaS在室温下的荧光激发谱和荧光辐射谱。荧光激发谱由四个激发带构成 ,是由Eu2 + 的 4f7→ 4f55d跃迁和基质吸收所产生的。可见光激发下的荧光辐射谱是由一个极强的宽带和两个极弱的窄带构成 ,紫外光激发下的荧光辐射谱中不仅出现了以上三个辐射带 ,还出现了七个较强的窄带。这些荧光辐射带分别是由Eu2 + 的 4f65d → 4f7、Sm3 + 的 f→ f、Eu3 + 的 f→ f跃迁所产生的。研究还发现 ,当激剂浓度一定时 ,Eu2 + 的辐射带明显比Sm3 + 的辐射带强。     

Qβ measurements of 158, 159Pm , 159, 161Sm , 160-165Eu , 163Gd and 166Tb using a total absorption BGO detector

Q _β values of the neutron-rich isotopes of ^160-165Eu and ¹⁶³Gd were measured for the first time using a total absorption bismuth germanate (BGO) detector, and previously obtained data on ^{158, 159}Pm , ^{159, 161}Sm and ¹⁶⁶Tb were re-analyzed. These radioactive sources were prepared by an on-line mass separator (Tokai-ISOL) following the ²³⁸U (p,f reaction. The deduced Q _β values are the following: 6085(80)keV for ¹⁵⁸Pm , 3805(65)keV for ¹⁵⁹Sm , 5460(140)keV for ¹⁵⁹Pm , 4705(60)keV for ¹⁶⁰Eu , 5065(130)keV for ¹⁶¹Sm , 3705(60)keV for ¹⁶¹Eu , 5575(60)keV for ¹⁶²Eu , 4690(70)keV for ¹⁶³Eu , 3170(70)keV for ¹⁶³Gd , 6430(70)keV for ¹⁶⁴Eu , 5800(120)keV for ¹⁶⁵Eu , and 4695(70)keV for ¹⁶⁶Tb . Moreover, the deduced mass excesses and two-neutron separation energies ( S _2n values) were compared with those of the atomic mass evaluations and theoretical predictions.     

丙酮酸稀土配合物的红外光谱研究

研究了Ｙ,Ｌａ,Ｃｅ,Ｐｒ,Ｎｄ,Ｓｍ,Ｅｕ,Ｇｄ,Ｄｙ和Ｈｏ等１０种丙酮酸稀土配合物的ＦＴ－ＩＲ光谱;对４００～２０００ｃｍ＾－１的主要红外吸收谱峰进行了归属;２００～４－ｃｍ＾－１有３个随稀土原子序数递增峰位向高波数位移的谱带,可指认为ＲＥ－Ｏ伸缩振动吸收。红外光谱表明,丙酮酸以酸根形式采用螯合桥式三齿方式与稀土配位,某些谱峰有裂分或拓宽现象。配位键以离子键成分为主。     

First-principles studies of effects of interstitial boron and carbon on the structural,elastic, and electronic properties of Ni solution and Ni_3Al intermetallics

The effects of boron and carbon on the structural, elastic, and electronic properties of both Ni solution and Ni_3Al intermetallics are investigated using first-principles calculations. The results agree well with theoretical and experimental data from previous studies and are analyzed based on the density of states and charge density. It is found that both boron and carbon are inclined to occupy the Ni-rich interstices in Ni_3Al, which gives rise to a cubic interstitial phase. In addition,the interstitial boron and carbon have different effects on the elastic moduli of Ni and Ni_3Al. The calculation results for the G/B and Poisson's ratios further demonstrate that interstitial boron and carbon can both reduce the brittleness of Ni, thereby increasing its ductility. Meanwhile, boron can also enhance the ductility of the Ni_3Al while carbon hardly has an effect on its brittleness or ductility.     

稀土氨羧络合物的吸收光谱研究

本文系统地研究了EDTA,NTA,CyDTA,TTHA与镨,钕,钐,铕,锹,铒络合物的可见光吸收光谱及三阶导数光谱,并以Nd,Ho-TTHA体系测定了混合稀土氧化物中的Nd,Ho,首次以Sm-DTPA体系的三阶导数我谱成功地进行了纯氧化镧中杂质氧化钐的测定。     

Structural changes in RNiO3 perovskites (R=rare earth) across the metal–insulator transition

Rare earth nickel oxide perovskites (RNiO₃, R=rare earth) have, except for LaNiO₃, a metal–insulator (MI) phase transition as temperature decreases. The transition temperature (T_MI) increases as the R-ion becomes smaller. They also present, at low temperatures, a complex antiferromagnetic order. For lighter R-ions (e.g. Pr and Nd), the antiferromagnetic transition temperature (T_N) is close to T_MI, while for heavier R-ions (e.g. Eu, Sm), T_MI and T_N are very far apart, suggesting that the magnetic and electronic behaviors are not directly coupled. Even though Ni³⁺ is a Jahn–Teller ion, no distortion in the NiO₆ octahedra was found for RNiO₃ perovskites with R=Pr, Nd, Sm and Eu. In this work we have measured EXAFS at Ni K edge for samples of PrNiO₃, NdNiO₃ and EuNiO₃. The Fourier transform spectra for the three samples show a clear splitting in the first peak at the insulating phase. This splitting corresponds to two or more different Ni–O distances. This indicates that there is either a distortion in the NiO₆ octahedra or there are two different Ni sites at the insulating phase.     

Glass formation and microstructure evolution in Al–Ni–RE (RE = La,Ce, Pr,Nd and misch metal) ternary systems

Glass formation has been systematically studied in melt-spun Al-rich Al–Ni–RE (RE?=?La, Ce, Pr, Nd and Mm; Mm?=?misch metal) alloys by navigating the compositions following the observation of microstructure evolution in the resulting ribbons. The optimum glass-forming regions are similarly located around Al₈₅Ni₁₀RE₅ and found in the centre of the composites with primary phase α-Al, Al₁₁RE₃ and Al₃Ni. The similarities in the critical cross-section below which a component is fully amorphous and the optimum compositions in these Al–Ni–RE systems are interpreted in terms of their competing crystalline phases and thermodynamic properties. Interestingly, it is indicated that Ni content is markedly higher than RE content in the best glass-forming alloys, which may be associated with strong interaction between Ni–Al atom pairs and the dense packing due to Ni-centred clusters.     

Influence of the magnetic field strength and excitation intensity on the shape of microphotoluminescence spectra of quantum-well structures based on GaN/InGaN doped with Sm and Eu + Sm

This paper presents the results of complex measurements of the microphotoluminescence spectra of quantum-well structures based on InGaN/GaN〈Sm〉 and the determination of the concentration and charge state of the Sm dopant. It has been shown that an increase in the magnetic field strength and the excitation intensity of the microphotoluminescence spectra leads to an increase in the luminescence intensity and a shift in the position of the maximum of the emission wavelength toward the short-wavelength region of the spectrum. Measurements of the microphotoluminescence spectra with variations in the external magnetic field strength, as well as with the introduction of paramagnetic and magnetic impurities, provide additional information on the mechanisms of formation of luminescence spectra in the quantum-well structures InGaN/GaN〈Sm〉,〈Eu + Sm〉. In the long-wavelength region, the influence of the magnetic field on the shape of the microphotoluminescence spectra of the InGaN/GaN structures doped with Sm and Sm + Eu is less pronounced than that in the short-wavelength region.     

Dipole bands in nucleus ~(139)Pm

High-spin states in nucleus 139Pm have been studied using the reaction 116Cd(27Al,4n)139Pm.Two dipole cascades have been found.Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei(DCO) ratios and systematic behavior in neighboring odd-proton nuclei.The level structures of 139Pm are compared with those of the N =78 isotone 141Eu in which two dipole bands have been confirmed as magnetic rotational bands.The close similarity between them suggests that the dipole bands in 139...     

Spin dynamics and structural phase transitions in quasi-2D antiferromagnets R2CuO4 (R=Pr, Sm, and Eu)

Spin and lattice dynamics of R₂CuO₄ (R=Pr, Sm, and Eu) crystals were studied over the frequency and temperature ranges 20–250 GHz and 5–350 K, respectively. The absorption coefficients of the R₂CuO₄ crystals (R=Pr, Sm, and Eu) were found to change dramatically at temperatures of, respectively, 20, 80, and 150 K over a broad frequency range above 120 GHz. The absorption jumps were caused by the structural phase transitions. Broad spin-wave bands were observed in the high-temperature phases of all crystals studied. Absorption lines due to lattice dynamics were observed near the temperatures of structural phase transition over a broad frequency range, including the frequencies corresponding to the spin-wave bands.     

轻稀土与苯基乙酰甲基亚砜配合物的合成表征及光致发光

合成了五种轻稀土高氯酸盐与苯基乙酰甲基亚砜(L)的配合物RE(C1O₄)·L₅·2H₂O(RE=La,Pr,Nd,Sm,Eu),该系列配合物可溶于水,红外光谱及摩尔电导表明,配体通过亚砜基团上的氧原子与稀土离子配位,羰基氧不参与配位,３个高氯酸根离子有2个在内界与稀土离子配位,另1个在外界不参与配位。测定了配体的磷光光谱,并对配合物进行了热重和核磁共振氢谱等表征。铕(Ⅲ)配合物荧光光谱表明,Eu3+处于无反演对称中心格位上,且该配合物的发光机理属于M→M型发光。     

Skeletal vibrations of cuprate superconductor-like phases: a comparison of the FT-FIR spectra of La2−x Sr x CuO4, Nd2−x Ce x CuO4 and RBa2 Cu3 O7−x (R=Ln or Y) Powders

Il Nuovo Cimento D - The FT-IR/FT-FIR spectra of powders of Nd2−x Ce x CuO4 and La2−x Sr x CuO4 solid solutions and of RBa2Cu3O7−x with R=Y, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm and...     

(REO)3BO3(RE=La、Gd、Y)中Pr3+的光致发光

研究了紫外光激发下,（ＲＥＯ）３ＢＯ３（ＲＥ＝Ｌa、Ｇd、Ｙ）基质中Ｐr＾３＋的光 谱性质;探讨了基质晶格、阳离子半径、Ｐr＾３＋－Ｏ＾２－键的共价性等因素对光谱性 质的影响;分析了Ｐr＾３＋的发光强度随组成变化的规律性及Ｐr＾３＋的＾３Ｐ１→＾３Ｆ２跃迁发射的自身浓度猝灭机理。