Abstract
It is demonstrated that the linear muffin-tin orbital (LMTO) method used with interstitial spheres can provide accurate structural energy differences involving the open-packed diamond and simple-cubic (sc) structures. The total-energy differences calculated between these two structures in this manner, and between these and more conventionally LMTO calculated fcc, hcp, and bcc structures, are seen to be in excellent agreement with the highly accurate results of Yin and Cohen for both carbon and silicon. The agreement persists over a wide range of volume, including the prediction of a high-pressure diamond to sc transition in carbon, in the absence of intermediate phases.