评“半导体纳米晶体的自净化”
Comment on "Self-Purification in Semiconductor Nanocrystals"
摘要：
在最近的一封信[PRL 96，226802（2006）]中，Dalpian和Chelikowsky声称，在CdSe纳米晶体中Mn杂质的形成能随着尺寸的减小而增加，并且认为这种尺寸依赖性导致小纳米晶体的“自纯化”。他们提出了密度泛函理论（DFT）计算，显示了Mn杂质形成能量的强烈尺寸依赖性，并提出了一个一般性的解释。在这篇评论中，我们表明，几个不同的DFT代码，赝势，交换相关泛函给出了一个显着不同的结果：我们发现没有这样的大小依赖性。更一般地说，我们认为，形成能是不相关的替代掺杂在大多数胶体生长的纳米晶体。
英文摘要：
In a recent Letter [PRL 96, 226802 (2006)], Dalpian and Chelikowsky claimed that formation energies of Mn impurities in CdSe nanocrystals increase as the size of the nanocrystal decreases, and argued that this size dependence leads to "self-purification" of small nanocrystals. They presented density-functional-theory (DFT) calculations showing a strong size dependence for Mn impurity formation energies, and proposed a general explanation. In this Comment we show that several different DFT codes, pseudopotentials, and exchange-correlation functionals give a markedly different result: We find no such size dependence. More generally, we argue that formation energies are not relevant to substitutional doping in most colloidally grown nanocrystals.
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