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First principles study on elastic properties and phase transition of NpN

第一原理計算による窒化ネプツニウムの弾性特性と相転移評価

柴田 裕樹; 都留 智仁; 平田 勝; 加治 芳行

Shibata, Hiroki; Tsuru, Tomohito; Hirata, Masaru; Kaji, Yoshiyuki

密度汎関数理論に基づく第一原理計算によりマイナーアクチノイド窒化物の一つである窒化ネプツニウムの機械特性についてスピン軌道相互作用を考慮して評価した。非磁性(NM),強磁性(FM),反強磁性(AFM)それぞれの磁性のNaCl, CsCl, ZnS結晶構造の機械的安定性を調べたところ、すべての磁性状態のNaCl構造とスピン軌道相互作用を考慮しない非磁性状態を除いたZnS構造が安定であることが明らかとなった。そして、安定構造の体積弾性率,弾性係数,ヤング率,ポワソン比と異方性パラメータを算出した。それぞれの構造のエンタルピーの圧力依存性から、窒化ネプツニウムでは-7.32GPaでZnS構造からNaCl構造に相転移することが明らかとなった。

The mechanical properties of neptunium nitride (NpN) were investigated using first principles calculations based on density functional theory that take the Spin-Orbit Coupling (SOC) effect into consideration. With NaCl, CsCl and ZnS structures in nonmagnetic (NM), ferromagnetic (FM) and antiferromagnetic (AFM) states, the structure of NaCl in all magnetic states and that of ZnS, excluding the NM state without SOC, were found to be mechanically stable. The bulk moduli, elastic constants, Young's moduli, Poisson's ratios and anisotropic factors of NpN in stable states were also estimated. The enthalpies of NpN for NaCl and ZnS structures revealed that the phase transition of NpN from ZnS structure to NaCl structure took place at a pressure of -7.32 GPa, and hence the phase transition of NpN in a cubic system does not occur at positive pressure.

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パーセンタイル:23.83

分野:Materials Science, Multidisciplinary

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