Significance of Non-Linear Terms in the Relativistic Coupled-Cluster Theory in the Determination of Molecular Properties

Abstract

The relativistic coupled-cluster (RCC) theory has been applied recently to a number of heavy molecules to determine their properties very accurately. Since it demands large computational resources, the method is often approximated to single and double excitations (RCCSD method). The effective electric fields ( E e f f ) and molecular permanent electric dipole moments (PDMs) of SrF, BaF, and mercury monohalides (HgX with X = F, Cl, Br, and I) molecules are of immense interest for probing fundamental physics. In our earlier calculations of E e f f and PDMs for the above molecules, we neglected the non-linear terms in the property evaluation expression of the RCCSD method. In this work, we demonstrate the roles of these terms in determining the above quantities and their computational time scalability with the number of processors of a computer. We also compare our results with previous calculations that employed variants of RCC theory, as well as other many-body methods and available experimental values.

Towards CP -violation studies on superheavy molecules: Theoretical and experimental perspectives

“…We employ the UTCHEM [45,46] package for DHF calculations and for atomic orbital to molecular orbital integral transformations and, in tandem, use the DIRAC08 package for RCC calculations [47]. We finally use our expectationvalue code to evaluate the values of the properties [48]. We present the calculated values of E eff , W s , their ratios, and μ of LrO, LrF + , and LrH + from the DHF and RCCSD methods in Table I.…”

“…We propose to use the RIKEN heavy-ion linear accelerator (RILAC) facility because a high-intensity ion beam is readily available to produce the atoms of interest. As for 256 Lr production, we propose the 209 Bi( 48 Ca, 1n) reaction as a possible candidate, for which a production cross section of 60 nb has been reported [65], although it is necessary to have a stable supply of 48 Ca. As explained in Ref.…”

Towards CP Violation Studies on Superheavy Molecules: Theoretical and Experimental Perspective

“…We employ the UTChem [41,42] package for DF calculations and for atomic orbital to molecular orbital integral transformations, and in tandem, use the Dirac08 package for RCC calculations [43]. We finally use our expectation value code to evaluate the values of the properties [44]. We present the calculated values of E eff , W s and µ of LrO, LrF + , and LrH + from the DF and RCCSD methods in Table I.…”

Electric dipole moments and the search for new physics

“…For spherical nuclei, the MQM is roughly independent of Z, while for quadrupole-deformed nuclei there is a collective enhancement [216][217][218] which scales roughly as M ∝ Z 2/3 . The structure-dependent factors q require detailed calculations of electron or nuclear wavefunctions in order to evaluate [195,[219][220][221][222][223][224][225][226][227][228][229][230][231][232][233][234][235]. For electrons in atoms/ions, q at is largest for systems where s and p orbitals are the main components of the states mixed by the external (for atoms) or internal (for ions in a molecule) E-field.…”