Thank you for the reply! Now I know the reason why it's shifted. I didn't
understand it well.
However, I don't understand yet why lammps doesn't use a simple linear
the keyword 'linear'? If we could have that large amount of input data, I
expect a simple
linear interpolation gives a better fitting. Due to the splining, both
'spline' and 'linear' table
style do not produce a fitted curve exactly crossing all the original data
points. You can
see this if you zoom in the plot even you think the fitting is good enough.
linear interpolation can at least pass all the original data points, which
should be trusted
for a known function or when you trust your input data. For unknown function
cannot say the original data are always trustable than the fitted ones. But
I don't see
a way to do this in lammps. (lookup method is not good, it makes step