$addrefbias

$addrefbias is to determine the additional bias in the simulation.

It is similar to the $sourcebias, where is a fixed value is used. This is for the system that has 4 or more contacts.

For example

$addrefbias
0.1 

This means that the bias of the reference contact is at 0.1V.

The $addrefbias setting in GUI interface is here
Press Contact Setting and fill in the field for the V-ref, remember to check the box below!