Bug #1527
mass contribution to dH/dlambda has wrong sign
Affected version - extra info:
Affected version:
Difficulty:
uncategorized
Description
Commit b8440aeb incorrectly change the sign of the kinetic contribution to dH/dl. The commit message says:
in update.c, in calc_ke_part_normal and calc_ke_part_visc
- sign error in mass change; if mass B is greater than mass A, then the
change in free energy is positive, not negative.
This is incorrect, if massB is greater the free-energy change is negative. The kinetic contribution is obtained from the derivative of p^2/(2*mass(lambda) which has the opposite sign.
The fix is only a sign change (plus a comment explaining this tricky sign issue).
Since mass contributions vanish is a thermodynamic cycle, I don't know if we should fix this for 4.6.6 or for 5.0.
Associated revisions
History
#1 Updated by Mark Abraham over 5 years ago
- Description updated (diff)
#2 Updated by Gerrit Code Review Bot over 5 years ago
Gerrit received a related patchset '1' for Issue #1527.
Uploader: Berk Hess (hess@kth.se)
Change-Id: Ia1a2f708cdbba9a5a120a2ba8510cc2498f4d054
Gerrit URL: https://gerrit.gromacs.org/3681
#3 Updated by Berk Hess over 5 years ago
- Status changed from New to Fix uploaded
- Target version set to 4.6.6
#4 Updated by Erik Lindahl over 5 years ago
- Status changed from Fix uploaded to Resolved
#5 Updated by Erik Lindahl over 5 years ago
- Status changed from Resolved to Closed
Fixed the sign of mass perturbed contribution
Corrected the sign of the kinetic energy contribution to dHdl and dH.
Fixes #1527.
Change-Id: Ia1a2f708cdbba9a5a120a2ba8510cc2498f4d054