Scientific article
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ß phase of Pb on Ge(111) : the competing roles of electronic bonding and thermal fluctuations

Published inPhysical review letters, vol. 71, no. 22, p. 3685-3688
Publication date1993

We have studied the low temperature phases of Pb/Ge(111) at Pb coverages Θ=1/3, 1, and 4/3 using ab initio molecular dynamics. Stable phases are found to occur at Θ=1/3 and 4/3. For the low-coverage (Θ=1/3) α phase, we confirm the model of Pb atoms adsorbed at T4 sites of the Ge(111) substrate. For the high coverage (Θ=4/3) β phase and very low temperature, we determine a structure characterized by the presence of covalently bonded Pb chains parallel to 〈11¯0〉 substrate directions. At room temperature, fluctuations are found to disrupt long-range Pb chains and restore the threefold symmetry of the ideal Ge(111) surface. The calculated structure factors and local density of states agree well with x-ray diffraction and STM data.

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ANCILOTTO, Francesco, SELLONI, Annabella, CAR, Roberto. ß phase of Pb on Ge(111) : the competing roles of electronic bonding and thermal fluctuations. In: Physical review letters, 1993, vol. 71, n° 22, p. 3685–3688. doi: 10.1103/PhysRevLett.71.3685
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ISSN of the journal0031-9007

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