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高温融体内の原子の運動に関する実験的な知見は、融体の熱物性と構造の関係を理解する上で極めて重要である。我々は、高温融液の原子ダイナミクスの観察を目的として非弾性X線散乱用の小型の静電浮遊装置を開発し、融点および過冷却液体シリコンの動的構造因子を測定した。本装置を用いることにより液体シリコンのフォノンピークが明瞭に観察され、その分散関係が明らかになった。, The atomic dynamics in high temperature melts are essential information for the understanding of the relation between liquid structure and thermo-physical properties in liquid state. The small Electrostatic Levitation furnace, ESL, was developed for the inelastic X-ray scattering facility in SPring-8. The observation of dynamic liquid structure factor, S (Q, w) of normal and undercooled liquid silicon was performed. The phonon peak of S (Q, w) in the liquid silicon was clearly observed and its dispersion relation can be obtained., 資料番号: AA0063323004, レポート番号: JAXA-RR-06-015E

An electrostatic levitator was developed for the structural analysis of high-temperature and undercooled liquids by X-ray diffraction. The apparatus can be used to investigate the structure of metallic, semiconductor, and ceramic liquids. Samples of zirconium, silicon, and alumina in their liquid phases could be kept levitated for more than one hour with this apparatus. This was sufficiently long to perform a detailed analysis of the liquid structure by X-ray diffraction techniques., 資料番号: AA0063323003, レポート番号: JAXA-RR-06-015E

X線・中性子散乱法と静電浮遊炉を組み合わせることにより、超高温や過冷却液体の構造を精密に測定することが可能である。本研究は、シリコンやジルコニウムなど高温金属液体の液体構造を測定するために、構造解析用の静電浮遊炉を新たに開発し、高輝度放射光および中性子線を用いた散乱実験を試みた。実験の結果、これらの液体の静的構造因子(過冷却液体状態を含む)を高精度に測定することができた。, The structure of undercooling liquid state is one of the important subjects of materials science. The levitation techniques are powerful tools for the investigation of undercooled liquids. In this research, we developed the electrostatic levitation furnace for the liquid structure analysis due to the neutron and x-ray diffraction methods. The apparatus was tested by using a synchrotron radiation facility, a laboratory X-ray source and a reactor. The structures of several kinds of materials were investigated and the liquid structures can be measured with high precision., 資料番号: AA0049301004, レポート番号: JAXA-RR-05-034E

The containerless technique is one of the latest methods for the handling of matters at high temperature and in undercooled liquid states. In this research project, the electrostatic levitation technique has been applied to the structural analysis of liquids by using the neutron and X-ray scattering techniques. The current status of this subject is described briefly., 資料番号: AA0048709004, レポート番号: JAXA-RR-04-044E

The brief review is presented for the activity of the first IAO candidate plan [Roles of the short range order on the self- and impurity diffusion of liquid group 14(4B) elements with a different degree of complexity]. Various theoretical tools, liquid theories, molecular dynamics coupled with the X-ray and neutron scattering analysis indicate that the effect of covalent bond may remain to be present in liquid Ge though its structure is loosely packed. The shear cell technique was polished up. In situ observation system was established. Based on these activities, the present first IAO plan is advancing successfully., 資料番号: AA0046917059

The velocity of sound was measured for liquid Sn and liquid Sn based alloys containing Pb in the temperature range from 500 K to 1,040 K. The adiabatic compressibility and the isothermal compressibility were obtained. Finally the structure factor in the long wave length limit was evaluated. The effect of the addition of Pb is rather small for these quantities. This indicates that the substitutional model can be valid in this dilute Pb concentration range., 資料番号: AA0045399009, レポート番号: NASDA-TMR-020025E

The structure factors, S(Q), of liquid tin was obtained by neutron diffraction last year. Analysis of this S(Q) was performed in comparison with the use of hard sphere model. The radial distribution function g(r) was calculated from the S(Q), then the first coordination numbers were estimated by the standard regime., 資料番号: AA0045399002, レポート番号: NASDA-TMR-020025E

液体ゲルマニウムに対する分子動力学シミュレーションの結果を報告した。Stillinger-Weberにより始めて提案された2体および3体の相互作用を含む経験的原子間ポテンシャルを使用した。シミュレーションによって得た拡散係数と静的液体構造を実験結果と比較した。分子動力学によって見積もった拡散係数は、微小重力下で得た実験データよりも小さくなった。シミュレーションによる動径分布関数は、明らかに大きすぎる2乃至3個のピークを持っている。シミュレーションと実験の間の液体構造の一致を向上するために、原子間ポテンシャルパラメータの修正をおこなった。その結果、拡散係数は増大し、液体構造は実験データに近づいた。, The results of molecular dynamics simulations for liquid Ge were presented. The empirical interatomic potential, originally proposed by Stillinger-Weber, which includes two- and three- body interactions, was employed. The diffusion coefficient and the static liquid structure obtained by the simulations were compared with results derived from experiments. The diffusion coefficients estimated by molecular dynamics become smaller than experimental data obtained in microgravity. The radial distribution function resulting from the simulations displays clearly too larger second and third peaks. Adjustment of the interatomic potential parameter was tried to improve the agreement of liquid structure between simulations and experiments. As a result, the diffusion coefficients became larger and the liquid structure closer to the experimental data., 資料番号: AA0029039014, レポート番号: NASDA-TMR-000013E

中性子散乱実験により573、773および1,073Kの温度における液体すずの構造を研究した。573Kにおける構造因子S(Q)の第1ピークの高-Q側に明瞭にショルダーを観測した。温度の上昇と共に、S(Q)の全体形状の変化のためショルダーの存在は明瞭ではなくなるが、このショルダーに関係する構造は1,073Kの温度でも残存しているように見える。ab initio分子動力学法を用いて、液体すずに対して計算機シミュレーションを行った。計算結果は中性子実験で求めたS(Q)を充分に再現した。さらに、液体すずの3体分布関数における角度分布の解析から、幾つかの4面体ユニットのフラグメントが存在することが分かった。, The structure of liquid tin was studied at temperatures of 573, 773 and 1,073 K by neutron scattering experiments. A shoulder was clearly observed in the high-Q side of the first peak of the structure factor S(Q) at 573 K. Though with increasing temperature the existence of the shoulder becomes less clear due to the change of the overall shape of S(Q), the structure related to this shoulder seems to remain even at 1,073 K. Computer simulations for liquid tin were carried out using an ab initio molecular-dynamics method. The calculated results well reproduced S(Q) obtained by the neutron experiments. Moreover, the existence of some fragments of the tetrahedral unit was shown from an analysis of the angle distribution in the three-body distribution function of liquid tin., 資料番号: AA0029039012, レポート番号: NASDA-TMR-000013E

以下の主題を論じた。液体金属の剛体球模型、液体の精密化理論、液体リチウムの分子動力学シミュレーション、剛体球流体の自己拡散、液体リチウムの同位体効果、高反応性液体金属の微小重力拡散、Ag-Cu合金の拡散、液体すずの構造、液体すずとゲルマニウムの有効対ポテンシャル、拡散測定用せん断セル法、液体シリコンの濡れ性と反応、拡散実験に及ぼす凝固効果、および拡散試料中の対流の解析。, The following topics were discussed: hard sphere model of liquid metal, refined theory of liquid, molecular dynamics simulation of liquid lithium, self-diffusion of hard sphere fluids, isotope effect of liquid lithium, microgravity diffusion of highly reactive liquid metals, diffusion of Ag-Cu alloys, structure of liquid tin, effective pair potential of liquid tin and germanium, shear cell method for diffusion measurement, wettability and reaction of liquid silicon, solidification effects on diffusion experiments, and analysis of convection in diffusion sample., 資料番号: AA0029039000, レポート番号: NASDA-TMR-000013E

液体内の物質移動の機構を明らかにするため単純液体金属の分子動力学シミュレーションを行った。分子動力学シミュレーションでは、剛体球流体の自己拡散に対するSpeedyの式の有効性を検討した。剛体球流体の数値模型として無次元形の方程式を記述した。充填率、拡散係数、Enskogの式およびSpeedyの式を定義し、拡散係数とEnskogの式に基づき後方散乱係数を計算した。剛球体系は充填率に依存して液体または固体としての性質を示す。液体と固体間の遷移状態は充填率だけではなく初期条件にも左右されることが分かった。Boublik-Nozbeda方程式に基づいて遷移状態を論じ、また、本分子動力学シミュレーションの有効性を明らかにした。剛球体系の液体構造を動径分布関数の形で評価した。本剛球体系の構造は液状であるように見られ、液相に特有の振動が存在する。無次元拡散係数と後方散乱係数の充填率への依存度を計算した。拡散係数は充填率が0.05〜0.45の範囲でSpeedyの式と一致した。, The molecular dynamics simulation of simple liquid metals was carried out in order to clarify the mechanism of mass transfer in liquids. In the molecular dynamics simulation, the validity of Speedy et al's formula for self-diffusion of hard sphere fluids was studied. Equations in non-dimensional forms were written for numerical modeling of hard sphere fluid. Packing fraction, diffusion coefficient, Enskog's formula and Speedy's formula were defined respectively. The back scattering factor was calculated based on the diffusion coefficient and Enskog's formula. The hard sphere system behaves as a liquid or a solid depending on the packing fraction. Transition state between liquid and solid is found not to depend on only the packing fraction but also on the initial conditions. The transition state was discussed based on Boublik-Nozbeda equation, and the validity of the present molecular dynamic simulation was shown. The liquid structure of the hard sphere system was evaluated in the form of radial distribution function. The structure of present hard sphere system seems to be liquid like and there exists a specific oscillation in liquid phase. The dependence of the non-dimensional diffusion coefficient and the back scattering factor on packing fraction was calculated. The diffusion coefficient agreed with the Speedy's formula over the packing fraction range 0.05 to 0.45., 資料番号: AA0029039004, レポート番号: NASDA-TMR-000013E

資料番号: AA0063323000, レポート番号: JAXA-RR-06-015E

資料番号: AA0045399000, レポート番号: NASDA-TMR-020025E