diff --git a/doc/src/pair_fep_soft.txt b/doc/src/pair_fep_soft.txt index 864aebdedd..06781d07f0 100644 --- a/doc/src/pair_fep_soft.txt +++ b/doc/src/pair_fep_soft.txt @@ -319,13 +319,14 @@ interaction. NOTE: The analytical form of the tail corrections for energy and pressure used in the {lj/cut/soft} potentials are approximate, being identical to that of the -corresponding non-soft potentials scaled by a factor lambda^n. For real-space -cutoffs greater than 2.5 sigma and alpha_LJ = 0.5, the error affecting the tail -correction is below 0.2% when lambda = 0 (worse case). This error disappears as -lambda approaches 1. Note that this is the error affecting the long-range tail -(itself a correction to the interaction energy) which includes other -approximations, namely that the system is homogenous (local density equal the -average density) beyond the cutoff. +corresponding non-soft potentials scaled by a factor lambda^n. The errors due to +this approximation should be negligible. For example, for a cutoff of 2.5 sigma +this approximation leads to maximum relative errors in tail corrections of the +order of 1e-4 for energy and virial (alpha_LJ = 0.5, n = 2). The error vanishes +when lambda approaches 0 or 1. Note that these are the errors affecting the +long-range tail (itself a correction to the interaction energy) which includes +other approximations, namely that the system is homogenous (local density equal +the average density) beyond the cutoff. The {morse/soft} pair style does not support the "pair_modify"_pair_modify.html tail option for adding long-range tail corrections to energy and pressure.