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Kawakita, Yukinobu; Kikuchi, Tatsuya*
Hamon, 29(2), p.91 - 94, 2019/05
Bismuth (Bi) has a double-layered structure based on Peierls distortion in crystalline phase. Complicated static structure in liquid phase which cannot be interpreted by a simple packing model has been conjectured that Peierls distortion may remain even in liquid phase. We measured quasi-elastic neutron scattering (QENS) of liquid Bi by using AMATERAS installed at BL14 beamport of Materials and Life Science Experimental Facility (MLF) in J-PARC and analyzed coherent QENS spectra. A time-space correlation function revealed that the nearest neighboring shell followed by a shoulder-like structure at longer side consists of four contributions of short and long correlations with relatively long relaxation time of a few tens pico second and medium-ranged and the longest correlations with a short relaxation time of sub-pico second, which is a direct observation of the existing layered structure in liquid Bi. In this article, we report the above scientific results and the method to analyze coherent QENS by the time-space correlation function.
Kikuchi, Tatsuya
no journal, ,
Dynamic structure factor, S(Q,E), which can be obtained by Inelastic neutron scattering directly, is a function of scattering vector, Q, and energy transfer, E. In recent years, importance of the studies on dynamics that cannot be well described by Q and E in substances such as battery materials has increased. S(Q,E) is defined as a Fourier-transformed function from van Hove's space-time correlation function, G(r,t), which is a function in real space and time. G(r,t) is important to express local motions of atoms and molecules directly on these substances. However, the calculation of G(r,t) has been hardly performed even though it is so easy mathematically, because it requires spectrum in both high resolution and wide range in Q-E space. By the progress of the recent neutron sources and spectrometers, the measurements with wide range and high resolution in Q-E space are becoming easy. We measured high-resolution S(Q,E)s using AMATERAS spectrometer installed at J-PARC and calculated G(r,t)s. We used the maximum entropy method to lower the bias of truncation errors for the calculation of G(r,t).
Kawakita, Yukinobu; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Inamura, Yasuhiro; Nakajima, Kenji; Kawamura, Seiko; Arai, Masatoshi*
no journal, ,
no abstracts in English
Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.
no journal, ,
We have performed coherent quasielastic neutron scattering experiment for liquid polyvalent metals which has complicated static structure not reproduced by a hard-sphere packing model, by utilizing AMATERAS spectrometer in J-PARC. It has been considered that, for Bi and Sb, a double-layered structure originated from Peierls distortion which is seen in solid crystalline phase remains even in their liquid phases. We have succeeded in detection of such Peierls distortion structure in liquid by difference in structural relaxation time at corresponding charateristic interatomic distances in the deduced time-space correlation function.
Kawakita, Yukinobu; Kikuchi, Tatsuya*; Inamura, Yasuhiro; Tahara, Shuta*; Maruyama, Kenji*; Hanashima, Takayasu*; Nakamura, Mitsutaka; Kiyanagi, Ryoji; Yamauchi, Yasuhiro*; Chiba, Kaori*; et al.
no journal, ,
We have developed analysis method to reduce the so-call van Hove function, a time-space correlation function, through the regularization method for coherent quasielastic neutron scattering (QENS) of liquids. In principle, the van Hove function in r-t space can be obtained by double Fourier transform from dynamic structure factor in Q-E space. Instead of a direct function estimation of the van Hove function through the regularization method which easily involves systematical deviation of the calculated dynamic structure factor from the experimental dynamic structure factor, we used a mediation function between them and estimated it through the regularization method. We will discuss with the properties of the mediation function and the obtained van Hove function and the calculated dynamic structure factor with an example of liquid metals with complex static structure such as Bi and Sb whose QENS were measured by AMATERAS spectrometer in J-PARC.
Kawakita, Yukinobu; Kikuchi, Tatsuya*
no journal, ,
There are polyvalent monatomic metals which a layered structure based on Peierls distortion in solid phase is suggested to remain even in liquid phase, for example, liquid Bismuth, Antimon and so on. Such a liquid structure has a complicated local structure where a relatively strong correlations of intra-layer and a weak correlations of inter-layer alternatively locate. Since many coordination shells of the first and second neighbors of the intra-layer and those of the inter-layer are superposed in the local structure, it is difficult to distinguish these shells only from static structure analysis, which has prevented us to confirm the layered structure in liquid. In such case, adding another axis of relaxation time can help us distinguish them from difference in relaxation time between the intra-layer and inter-layer correlations. We developed a new reduction method of a time-space correlation function from neutron scattering spectrum by applying the regularization method and elucidated that Peierls distortion structure exists in liquid.
Kawakita, Yukinobu; Kikuchi, Tatsuya*; Matsuura, Masato*; Kawasaki, Takuro; Kofu, Maiko; Tahara, Shuta*
no journal, ,
Materials and Life Science Experimental Facility (MLF) at J-PARC gives opportunities to use pulsed neutron beam to material science including fast ionic diffusion phenomena. DNA and AMATERAS spectrometers in MLF are quite useful to study atomic diffusion directly by quasielastic neutron scattering. We will focus relatively new analysis and experimental methods in this presentation such as mode distribution analysis and deduction of time-space correlation function which are both model free analysis, and possibility to detect an ionic channel in single crystal, with a few examples.
