New cubic phase of Li3N: stability of the N3- ion to 200 GPa.
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.
Lazicki
A
A
Lawrence Livermore National Laboratory, California 94550, USA.
Maddox
B
B
Evans
W J
WJ
Yoo
C-S
CS
McMahan
A K
AK
Pickett
W E
WE
Scalettar
R T
RT
Hu
M Y
MY
Chow
P
P