The formation of the plastic crystal phase in several pentaerythritol derivatives

In the calculation on the crystal structure of urea oxalic acid (2:1) (Harkema, Bats, Weyenberg & Feil, 1972) a wrong set of cell constants was used. The correct values for the cell constants are: a=5.110 (3), b= 12.400 (3), e= 7.035 (2), f l= 98.13 (7) °. The error has no appreciable effect on atomic positional parameters. The reported U values can easily be corrected for the difference in cell constants. Changes in bond angles and distances for some bonds are significant; therefore, corrections to Tables 4 and 5 in our paper are given.