Lazicki A, Maddox B, Evans W J, Yoo C-S, McMahan A K, Pickett W E, Scalettar R T, Hu M Y, Chow P
Lawrence Livermore National Laboratory, California 94550, USA.
Phys Rev Lett. 2005 Oct 14;95(16):165503. doi: 10.1103/PhysRevLett.95.165503.
Diamond-anvil cell experiments augmented by first-principles calculations have found a remarkable stability of the N(3-) ion in Li3N to a sixfold volume reduction. A new (gamma) phase is discovered above 40(+/-5) GPa, with an 8% volume collapse and a band gap quadrupling at the transition determined by synchrotron x-ray diffraction and inelastic x-ray scattering. gamma-Li(3)N (Fm3m, Li(3)Bi-like structure) remains stable up to 200 GPa, and calculations do not predict metallization until approximately 8 TPa. The high structural stability, wide band gap, and simple electronic structure make this N(3-) based system analogous to lower valency compounds (MgO, NaCl, Ne), meriting its use as an internal pressure standard.
通过第一性原理计算辅助的金刚石对顶砧细胞实验发现，Li3N 中的 N(3-)离子在体积缩小六倍时具有显著的稳定性。在 40(±5) GPa 以上发现了一种新的γ相，通过同步加速器 X 射线衍射和非弹性 X 射线散射确定，在转变时体积坍塌 8%，带隙增加四倍。γ-Li(3)N（Fm3m，类 Li(3)Bi 结构）在高达 200 GPa 时仍保持稳定，计算预测直到大约 8 TPa 才会发生金属化。这种基于 N(3-)的系统具有高结构稳定性、宽带隙和简单的电子结构，类似于低价化合物（MgO、NaCl、Ne），值得用作内部压力标准。
