Static electric dipole moments of nondegenerate systems probe mass scales for physics beyond the Standard Model well beyond those reached directly at high energy colliders. Discrimination between different physics models, however, requires complementary searches in atomic-molecular-and-optical, nuclear and particle physics. In this report, we discuss the current status and prospects in the near future for a compelling suite of such experiments, along with developments needed in the encompassing theoretical framework.

No abstract

No abstract

Relativistic study of xenotime, YPO4, containing atoms thorium and uranium as point defects is performed in the framework of cluster model with using the compound-tunable embedding potential (CTEP) method proposed by us recently [1]. The Y-(PO4)6-Y'22-O'104 cluster for xenotime is considered, in which central part, [Y-(PO4)6] −15 , is the main cluster, whereas outermost 22 atoms of yttrium and 104 atoms of oxygen are treated as its environment and compose electron-free CTEP with the total charge of +15. The P and O atoms of the orthophosphate groups nearest to the central Y atom are treated at all-electron level. The central Y, its substitutes, Th and U, together with environmental Y atoms are described within different versions of the generalized relativistic pseudopotential method [2]. Correctness of our cluster and CTEP models, constructed in the paper, is justified by comparing the Y-O and P-O bond lengths with corresponding periodic structure values of the YPO4 crystal, both experimental and theoretical.Using this cluster model, chemical properties of solitary point defects, X = U, Th, in xenotime are analyzed. It has been shown that the oxidation state +3 is energetically more profitable than +4 not only for thorium but for uranium as well (∆E ≈ 5 eV) despite the notably higher ionic radius of U +3 compared to Y +3 , whereas ionic radii of U +4 and Y +3 are close. This leads to notable local deformation of crystal geometry around the U +3 impurity in xenotime and contradicts to widespread opinion about favorite oxidation state of uranium in such kind of minerals [3].

No abstract