Discrepency between in.elastic and slope of stress strain curves


I am deforming bcc iron using the tension file provided in the tutorial. Using an eam potential the slope of my stress strain curve (strained to 2% at same strain rate as tutorial) is inaccurate compared to experimental data. However, for other forcefield types (reaxFF/tersoff), the slope is much more accurate.

Moreover, when I run the in.elastic at 300K I get a totally different value. I know this script runs micro strains in several directions, and is different than a typical lab style tension test. Why are the numbers so different though?