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Approximation in tail correction better explained

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Agilio Padua 2019-01-25 15:04:52 +01:00
parent 06c8a67247
commit f2aab01e96
1 changed files with 8 additions and 7 deletions
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15
doc/src/pair_fep_soft.txt
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@ -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.