Electronic interactions in the expanded metal compound Li-NH3

• Published in: Physical review letters Vol. 89; no. 23; p. 236404
• Main Authors: Burns, C A, Giura, P, Said, A, Shukla, A, Vankó, G, Tuel-Benckendorf, M, Isaacs, E D, Platzman, P M
• Format: Journal Article
• Language: English
• Published: United States 02.12.2002
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.89.236404

Inelastic x-ray scattering was used to measure the plasmon as a function of electron density in liquid lithium ammonia as well as the low temperature solid phase. As the electronic density is lowered, electronic correlation effects cause the random-phase approximation (RPA) to break down, requiring more advanced theoretical treatments. The deviation from RPA becomes greatest at the lowest electronic densities. We also see evidence for decreased electronic screening as shown by an increase in the strength of the pseudopotential at lower concentrations. Plasmon behavior in the solid is similar to that of the heavier alkali metals, but surprisingly different than in the liquid.