Dabo Ismaila, Wieckowski Andrzej, Marzari Nicola
Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
J Am Chem Soc. 2007 Sep 12;129(36):11045-52. doi: 10.1021/ja067944u. Epub 2007 Aug 17.
We have studied the vibrational properties of CO adsorbed on platinum and platinum-ruthenium surfaces using density-functional perturbation theory within the Perdew-Burke-Ernzerhof generalized-gradient approximation. The calculated C-O stretching frequencies are found to be in excellent agreement with spectroscopic measurements. The frequency shifts that take place when the surface is covered with ruthenium monolayers are also correctly predicted. This agreement for both shifts and absolute vibrational frequencies is made more remarkable by the frequent failure of local and semilocal exchange-correlation functionals in predicting the stability of the different adsorption sites for CO on transition metal surfaces. We have investigated the chemical origin of the C-O frequency shifts introducing an orbital-resolved analysis of the force and frequency density of states, and assessed the effect of donation and backdonation on the CO vibrational frequency using a GGA+molecular U approach. These findings rationalize and establish the accuracy of density-functional calculations in predicting absolute vibrational frequencies, notwithstanding the failure in determining relative adsorption energies, in the strong chemisorption regime.
我们使用密度泛函微扰理论，在佩德韦-伯克-恩泽霍夫广义梯度近似下，研究了吸附在铂和铂-钌表面的一氧化碳的振动特性。计算得到的碳-氧伸缩频率与光谱测量结果高度吻合。当表面覆盖有单层钌时发生的频率偏移也得到了正确预测。对于频率偏移和绝对振动频率的这种一致性，由于局域和半局域交换关联泛函在预测一氧化碳在过渡金属表面不同吸附位点的稳定性时经常失败而显得更为突出。我们通过引入对力和频率态密度的轨道分辨分析，研究了碳-氧频率偏移的化学起源，并使用广义梯度近似加分子U方法评估了给予和反馈对一氧化碳振动频率的影响。这些发现合理化并确立了密度泛函计算在预测绝对振动频率方面的准确性，尽管在强化学吸附 regime 中确定相对吸附能时存在失败。
