EFFECT OF SURFACE STATES ON THE CHEMISORPTION OF HYDROGEN ON SEMICONDUCTORS.

The effect of surface states and electron correlations on the chemisorption of hydrogen on semiconductors is studied on the basis of the Anderson Hamiltonian. It is shown that, in the absence of surface states, the chemisorption energy calculated in the unrestricted Hartree-Fock approximation is equal to the exact energy of the chemisorption of hydrogen on the (111) germanium surface. A density similar 10**1**4 cm** minus **2 of surface states increases the chemisorption energy by 30% in the unrestricted Hartree-Fock approximation by 60% when the chemisoprtion energy is calculated by a perturbation theory. The correlation energy, i. e. , the difference between the exact chemisorption energy and the chemisorption energy evaluated in the unrestricted Hartree-Fock approximation is found to be 0. 53 eV, which represents 19% of the observed chemisorption energy DELTA E//e//x//p approximately equals 2. 8 eV.