Towards first-principles understanding of the metal-insulator transition in fluid alkali metals

By treating the electron-ion interaction as perturbation in the first-principles Hamiltonian, we have calculated the density response functions of a fluid alkali metal to find an interesting charge instability due to anomalous electronic density fluctuations occurring at some finite wave vector $\text{bi}Q$ in a dilute fluid phase above the liquid-gas critical point. Since $\mathrm{\mid }\text{bi}Q\mathrm{\mid }$ is smaller than the diameter of the Fermi surface, this instability necessarily impedes the electric conduction, implying its close relevance to the metal-insulator transition in fluid alkali metals.