Background:This research contribution is part of the project "Linking continental emergence and climatic evolution on the early earth". The aim of the project is to use stable isotopes of rear Earth elements in ancient marine sediments to reconstruct palaeoenvironment. Therefore, ab initio calculations were performed to understand isotope fractionation on a molecular scale from a theoretical perspective. 

The ab initio calculations contain reduced partition function ratios (as lnβ) for aqueous complexes of some light rear Earth elements (La, Ce, Nd). These values help to predict mass-dependent isotope fractionation of these elements in hydrous systems like seawater or hydrothermal fluids. In addition, lnβ values for mass-independent nuclear field shift effects for La-complexes and Ce oxidation reactions are included. Also, the data contains speciation models of rear Earth elements in hydrous systems to quantify their complexation and isotope fractionation with varying fluid pH and temperature.

The lnβ values were calculated from molecular frequencies and total energies derived from calculations using the software packages ORCA, and DIRAC on the high performance computing (HPC) cluster at James Cook University. The atomic coordinates of the input files were created in AVOGADRO. The lnβ values were calculated from molecular vibrations and energies. Speciation modelling was performed in PHREEQC with fluid parameters obtained from the MARHYS database.

This data record contains:

1 MS Excel (.xlsx) file containing ab initio calculations of aqueous complexes of rare Earth elements and speciation models of seawater and hydrothermal fluids.

A more detailed description of the methodology and results is available in the related publication.

Software/equipment used to create/collect the data: ORCA, DIRAC, PHREEQC