[lammps-users] question for universal

hello ,dear
i always be puzzled by the potential Cu_u3 and Cu_u6? and what do the
universal 3 or universal 6 in the head of this files mean? which
different is it when itused ?

P.S. i have a mistake suspicion of document of manual of lammps in
Vecocity command that state: "The ramp style is similar to that used
by the temperature ramp command. Velocities ramped uniformly from vlo
to vhi are applied to dimension vx, or vy, or vz. The value assigned
to a particular atom depends on its relative coordinate value (in dim)
from clo to chi. For the example above, an atom with y-coordinate of
10 (1/4 of the way from 5 to 20), would be assigned a x-velocity of
1.25 (1/4 of the way from 0.0 to 5.0). Atoms outside the coordinate
bounds (less than 5 or greater than 20 in this case), are assigned
velocities equal to vlo or vhi (0.0 or 5.0 in this case). "

First the command Temperature do not exist in new lammps version.
Second to example of ramp velocity computer ,i think following the
document the atom with y-coordinate of 10 is not 1/4 of the way from 5
to 20,but is 5/15=1/3,so the velocity should be 1.6666(1/3 of the way
from 0.0 to 5.0)

some reply is very be appreciated

The EAM potential files are ones I've acquired from different sources
over the years. I think the "universal" ones (u3, u6, etc) were part
of the original DYNAMO code. So you'd have to go back to the original
EAM papers to read about them.

The temperature ramp command is now compute temp/ramp. The
math for 1/3 vs 1/4 is wrong, as you indicate. I'll update the doc page.