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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Host effects on the optically active 4f and 5d levels of Ce~(3+) in garnets
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Host effects on the optically active 4f and 5d levels of Ce~(3+) in garnets

机译：宿主对石榴石中Ce〜（3+）旋光性4f和5d水平的影响

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摘要

When Ce~(3+) is doped in a garnet, it substitutes for some cations. The effect of the substitution on the optically active 4f and 5d levels of Ce~(3+) can be analyzed in terms of an undistorted substitution followed by a structural relaxation, but, whereas the contribution of the undistorted substitution can be predicted/calculated using the crystallographic structure of the pure garnet, which is at hand, that of the structural relaxation demands the detailed local structure around the Ce~(3+) impurity, which is hard to know. Hence the importance of knowing the role of the undistorted substitution. What we study in this paper is the role of the unrelaxed host effects on the 4f and 5d levels of Ce~(3+)-doped garnets (i.e. the interactions between Ce and the second and more distant neighbors). When they are added to the (previously studied) unrelaxed first-neighbor effects, they give the contributions of the undistorted substitutions. We performed spin-orbit coupling, relativistic, embedded cluster, wave function based ab initio calculations on the (CeO8)~(13-) cluster under the effects of the embedding potentials of 21 selected garnets of Si, Al, and Ga, which have been obtained in this work, using experimental unrelaxed structures of the pure garnets. The calculations reveal that the unrelaxed host effect: (1) produces a red shift of the first 4f → 5d transition and (2) is an important contribution to this transition which plays a very important role in differentiating the values it has in different garnet families. The unrelaxed host effect is found to be responsible for the low value of the first 4f → 5d transition in Ce~(3+)-doped Lu2CaMg2Si3O_(12). It is analyzed in terms of 5d and 4f centroid energy contributions and crystal field splitting contributions in the 21 doped garnets. The effect on the splittings of the 4f and 5d levels is also discussed. The undistorted host approximation is found to give reasonable comparison with experiments, so that it represents a relatively fast way to provide reliable ab initio information on the 4f and 5d levels of Ce~(3+) in garnets.
机译：当Ce〜（3+）掺杂在石榴石中时，它可以代替某些阳离子。可以根据未扭曲取代后伴随结构弛豫来分析取代对Ce〜（3+）的旋光性4f和5d水平的影响，但是可以使用以下方法预测/计算未扭曲取代的贡献：纯石榴石的晶体结构，即结构弛豫的晶体结构，需要围绕Ce〜（3+）杂质的详细局部结构，这一点很难知道。因此，了解无失真替代的作用的重要性。我们在本文中研究的是未松弛的宿主效应对掺Ce〜（3+）石榴石的4f和5d水平的作用（即Ce与第二个或更远的邻居之间的相互作用）。当将它们添加到（先前研究的）未松弛的第一邻居效应中时，它们将给出未失真替换的作用。我们在（CeO8）〜（13-）团簇的21，Si，Al和Ga石榴石的嵌入电位的影响下，进行了自旋轨道耦合，相对论，嵌入式团簇，基于波函数的从头计算。通过使用纯石榴石的实验性非松弛结构获得了这项工作中获得的。计算表明，无松弛的宿主效应：（1）产生第一个4f→5d过渡的红移，（2）是对该过渡的重要贡献，在区分其在不同石榴石系列中的值时起着非常重要的作用。 。发现未松弛的宿主效应是掺杂Ce〜（3+）的Lu2CaMg2Si3O_（12）中第一个4f→5d跃迁的低值的原因。根据21d掺杂石榴石的5d和4f质心能量贡献和晶体场分裂贡献进行了分析。还讨论了对4f和5d水平分裂的影响。发现未失真的宿主近似值可与实验进行合理的比较，因此它代表了一种相对快速的方法，可提供有关石榴石中Ce〜（3+）4f和5d水平的可靠的从头算信息。

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