Pressure-dependent Knight shift in Na and Cs metal

We present an experimental and theoretical study of the pressure dependence of the Knight shift of ${}_{}{}^{23}{}_{}{}^{}\mathrm{Na}$ and ${}_{}{}^{133}{}_{}{}^{}\mathrm{Cs}$ in sodium and cesium metal, respectively. The sodium shift has been measured, employing the diamond-anvil cell technique, up to about 8 GPa, and our previous discovery of a shift minimum around 1.5 GPa has been confirmed. The temperature dependence of the shift results solely from thermal expansion. The cesium shift, at 295 K, increases by 74% between normal pressure and 2.1 GPa. The theoretical studies of the sodium shift are based on a self-consistent band structure calculation with the scalar-relativistic linear muffin tin orbital method and the local density approximation. Using an appropriate description of the volume dependence of the hyperfine field, our calculations lead to a correct prediction of the Knight shift minimum. Differences between spin-restricted and exchange-enhanced calculations are discussed. © 1996 The American Physical Society.