Ab initio Dirac-Hartree-Fock calculations of chemical properties and PT-odd effects in thallium fluoride

The theory of PT-odd interactions relevant to existing experimental measurements of the hyperfine structure of TlF is reviewed. We outline a relativistic electronic structure theory based on single-particle four-component Dirac spinors, and implemented using methods borrowed from ab initio quantum chemistry. Numerical calculations are reported of the electronic structure of TlF, some of its chemical properties, and of its PT-odd electronic matrix elements. From these results, and from published experimental data, we derive bounds on the value of the electric dipole moment of the proton, d_p, the tensor coupling constant C_T, and the Schiff moment of the ²⁰⁵Tl nucleus, Q, which are now the tightest available for these quantities. General issues regarding the calculation of the electronic structures of molecules containing heavy elements are also addressed.