[gmx-users] gmx msd unusual unit

[Joe Paul-Taylor]

Hello

With running gmx msd I am told in the output the y axis unit is nm/ S2/ N, which is unexpected. Is this simply an print error or is there an error within the calculation? I have provided a copy of the output below, noting the units of the self-diffusion coefficient are sensible. Any insight would be much appreciated.

# Created by:
#                       :-) GROMACS - gmx msd, 2019.2 (-:
# Command line:
#   gmx msd -s topol.tpr -f npt.xtc -b 3000 -e 13000 -o msd_IRMOF-NHPr_3OCT_8_run_1.xvg
# gmx msd is part of G R O M A C S:
#
# Gromacs Runs One Microsecond At Cannonball Speeds
#
@    title "Mean Square Displacement"
@    xaxis  label "Time (ps)"
@    yaxis  label "MSD (nm\S2\N)"
@TYPE xy
# MSD gathered over 10000 ps with 1001 restarts
# Diffusion constants fitted from time 1000 to 9000 ps
# D[       UNK] = 0.0031 (+/- 0.0004) (1e-5 cm^2/s)

Thank you

Joe