SURFACE-LAYER RELAXATION FOR BE(10(1)OVER-BAR0) - THEORY

We predict an inwards surface relaxation of the (<10(1)over bar 0>) su rface of Be. The surface layer relaxes inwards with 25% of the inter p lanar distance, a rather large value. However, the corresponding chang e of nearest-neighbour interatomic distances is smaller, of the order 2-6%. We show that the relaxation is correlated with a pronounced surf ace state in the vicinity of the Fermi level. By following the inward relaxation of the surface layer, we show that the total energy is lowe red mainly due to the one-particle energy. The most preferable termina tion of the Be(<10(1)over bar 0>) surface is shown to be the so-called A termination. Also, the termination of the Be(0001) is investigated and we conclude that the hcp termination is preferable compared to the fee termination.