Because of the equivocal status of variables such as first-phase density, which may be stored either slab-wise or whole-field, PHOENICS version 1.4 required that the references to the variables were made as AUX(DEN1) rather than DEN1, etc.
PHOENICS versions later than 1.5 do not need this: DEN1 will suffice, whichever mode of storage is used.
However, for the convenience of the users who desire that their version 1.4 coding should work with later versions, a function AUX is still provided: its value is the same as that of its argument.
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