As in the ADF main program, the unit of length can be set with the block type key
UNITS Length unit_of_length END
In densf the only item that can be specified in the UNITS block is the length, so it seems a bit pointless to make UNITS a block type key rather than a simple key. However, to make its usage identical to the application in the adf main program the block form has been chosen to apply also here. The unit-of-length will apply to the grid specification in the input file. Default is angstrom.
