U.S.-Italy Cooperative Research: Theoretical Investigation of the Lattice Dynamics of Clean Surfaces and Surfaces with Adsorbates

该奖项将支持加州大学欧文分校的Richard Wallis教授和Alexei Maradudin教授与意大利摩德纳大学的Virginio Bortolani教授合作进行的一项研究。研究人员打算把重点放在表面声子上，他们已经用非弹性氦原子散射技术测量了各种金属、绝缘体和半导体的色散曲线。他们打算进行一项协调一致的理论和计算工作，以提供铜、银和金表面声子线宽作为温度函数的值。所需的非调和参数将由已知的三阶弹性常数确定。研究人员还打算计算贵金属和面心立方过渡金属表面的声子色散曲线和特征向量。近年来，利用非弹性电子散射和非弹性氦原子散射测定广泛晶体表面声子色散曲线的实验研究取得了很大进展。后一种技术已经成功地应用于各种材料，并不断为表面动力学研究提供新的见解。这项拟议的合作将使美国研究人员受益于意大利研究人员在计算贵金属表面精确声子频率和特征向量方面的专业知识。反过来，美国方面将贡献其在计算表面声子线宽方面的专业知识，这源于他们研究晶体表面非谐波效应的综合计划。

This award will support Professors Richard Wallis and Alexei Maradudin of the University of California at Irvine in a research collaboration with Professor Virginio Bortolani of the University of Modena, Italy. The investigators intend to focus on surface phonons, whose dispersion curves have been measured for a wide variety of metals, insulators, and semiconductors by the inelastic helium atom scattering technique. They intend to carry out a concerted theoretical and computational effort to provide values for the surface phonon linewidths as functions of temperature for copper, silver, and gold surfaces. The required anharmonic parameters will be determined from the known third order elastic constants. The researchers also intend to carry out calculations of surface phonon dispersion curves and eigenvectors for surfaces of noble metals and face-centered-cubic transition metals. Much progress has been made in recent years in the experimental determination of surface phonon dispersion curves of a broad fange of crystal surfaces, using inelastic electron scattering and inelastic helium atom scattering. The latter technique has been applied with great success to a wide range of materials and keeps providing new insights into the study of surface dynamics. The proposed collaboration will enable the U.S. investigators to benefit from the expertise of the Italian investigators in calculating accurate phonon frequencies and eigenvectors for noble metal surfaces. The U.S.side will contribute in turn its expertise in calculating the linewidths of surface phonons, which stems from their comprehensive program studying anharmonic effects at crystal surfaces.