Ab-initio calculations of heavy-actinide hexahalide compounds: Do these heavy actinides behave as their isoelectronic lanthanide analogues? Cristian Celis-Barros, a∗ Day´ an P´ aez-Hern´ andez, a,b ∗ Maria J. Beltr´ an-Leiva, a Ramiro Arratia-Perez a,b ∗ a Relativistic Molecular Physics Group (ReMoPh), Universidad Andr´ es Bello, Rep´ ublica 275, Santiago, Chile. b Centro de Nanociencias Aplicadas, Universidad Andr´ es Bello, Rep´ ublica 275, Santiago, Chile. E-mail: cristian.andree@gmail.com\\dayan.paez@unab.cl Electronic Supporting Information Basis set performance in MOLCAS and ORCA Firstly, this study aims not only to reproduce accurately the scant experimental data available but also seeks to serve as a benchmark study by means of evaluating two different software platforms, namely MOLCAS and ORCA, in combination of different basis sets. Regrettably, MOLCAS has only one all-electron basis set available for metals heavier than curium called ANO-DK3, which is equivalent to a single-ζ basis set (see Computational Details). In spite of this limitation we tried a combination of this basis set with other ones for halogens such as ANO-MB, ANO-DZ and ANO-TZP. In the case of ORCA, the all-electron relativistic basis sets (SARC) were used at TZPP level in order to compare these results with those obtained by MOLCAS. In this way an insight on the scope and limitations of the available basis set for heavy actinides can be obtained. 1 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is © the Owner Societies 2017