In OpenMX Ver. 3.9, it is possible to contol the spin-orbit coupling strength using a conventional pseudopotential stored in the database Ver. 2019 without generating a special pseudopotential with a larger or smaller spin-orbit coupling. The scaling factors can be specified to each angular momentum quantum number by the following keyword:
<scf.SO.factor Ga s 1.0 p 2.0 d 1.0 f 1.0 As s 1.0 p 2.0 d 1.0 f 1.0 scf.SO.factor>The first column is the name of species which is defined by the keyword 'Definition.of.Atomic.Species', and followed by the subsequent columns: a symbol for angular momentum quantum number and a scaling factor. The '1.0' corresponds to the spin-orbit coupling strength in the channel with the angular momentum quantum number in the real atom. The set of information needs to be specified up to the f-channel for all the species in your system regardless of a kind of pseudopotentials.