Paraffin wax is currently used as an antirelaxation coating in alkali metal vapor cells since it prevents spin depolarization of alkali atoms. However, the performance of paraffin decreases rapidly above 80 ${}^{°}$C due to degradation; thus, the inability to operate at higher temperatures motivates a search for alternatives. Here, the authors use first-principles density functional theory to study rubidium (Rb) atom interactions with paraffin, along with potential alternative coating materials such as pristine and hydrogenated graphene, molybdenum disulfide, and the hydrogen-terminated silicon (111) surface. The authors’ results are in close agreement with experiments that find an adsorption energy of 0.1 eV for Rb on paraffin. The authors also find that Rb adsorbs strongly on graphene, MoS${}_2$, and silicon surfaces, but that Rb has a low adsorption energy on hydrogenated graphene, which may be suitable as an antirelaxation coating. The authors link adsorption behavior to the charge-transfer-induced ionic bonding between Rb and the underlying material. In paraffin and hydrogenated graphene, charge transfer is avoided, leading to low Rb adsorption energies for these materials.

中文翻译：

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评价抗松弛涂料的石蜡替代品

石蜡目前在碱金属蒸汽电池中用作抗松弛涂层，因为它可以防止碱原子自旋去极化。但是，石蜡的性能会在80以上迅速下降 ${}^{°}$C由于降解；因此，无法在更高的温度下运行促使人们寻找替代方案。在这里，作者使用第一原理密度泛函理论研究rub（Rb）原子与石蜡的相互作用，以及潜在的替代涂层材料，例如原始和氢化石墨烯，二硫化钼以及氢封端的硅（111）表面。作者的结果与发现石蜡上Rb的吸附能为0.1 eV的实验非常吻合。作者还发现，Rb在石墨烯，MoS上强烈吸附${}_2$，Rb和硅表面，但是Rb在氢化石墨烯上的吸附能很低，因此可能适合用作抗松弛涂层。作者将吸附行为与Rb和底层材料之间的电荷转移诱导的离子键相关联。在石蜡和氢化石墨烯中，避免了电荷转移，导致这些材料的Rb吸附能低。