Density of states in graphite from electrochemical measurements on ${\mathrm{Li}}_{\mathit{x}}$(${\mathrm{C}}_{1\mathrm{-}\mathit{z}}$${\mathrm{B}}_{\mathit{z}}$${)}_6$

Using electrochemical methods we have measured the variation of the chemical potential μ of intercalated Li in graphite and in boron-substituted graphite as a function of Li concentration x. For small x in ${\mathrm{Li}}_{\mathit{x}}$(${\mathrm{C}}_{1\mathrm{-}\mathit{z}}$ ${\mathrm{B}}_{\mathit{z}}$ ${)}_6$, μ can be predicted from the density of one-electron levels versus energy, and we find good agreement with the data for pure graphite and for a boron-doped sample. In the rigid-band model, dx/dμ vs μ is directly proportional to the density of states versus energy, and our measurements of dx/dμ agree well with empirical tight-binding density-of-states calculations. We show how the values of tight-binding overlap interactions can be directly determined from the electrochemical data.