[Wien] sign change in Mini

[Jack London]

Dear all 

Using "port" to minize 9 layers Pd(117) slab, I find
the force signs change from "positive" to "negtive" in
some step during the Minimization step (it does not
finish yet). So the force has a little bit
oscillation.  


:FOR001: 1.ATOM   21.231  7.775  0.155   19.756
:FOR001: 1.ATOM   21.230  7.611  0.150   19.818
:FOR001: 1.ATOM   14.736  5.304  0.135   13.748
:FOR001: 1.ATOM   5.597   0.440  0.244   5.574
:FOR001: 1.ATOM   2.194  -2.164  0.301  -0.200
:FOR001: 1.ATOM   4.510  -3.423  0.266  -2.925

:FOR002: 2.ATOM   4.994  -3.314  0.159   3.732
:FOR002: 2.ATOM   3.863  -2.554  0.161   2.894
:FOR002: 2.ATOM   3.161  -2.371  0.093   2.089
:FOR002: 2.ATOM   8.019   3.403  0.135   7.260
:FOR002: 2.ATOM  10.365   5.999  0.182   8.451
:FOR002: 2.ATOM   9.685   6.127  0.150   7.499

:FOR003: 3.ATOM  13.149  -5.650  0.462  11.864
:FOR003: 3.ATOM  12.744  -6.958  0.477  10.666
:FOR003: 3.ATOM   7.683  -1.765  0.153   7.476
:FOR003: 3.ATOM   6.239  -5.681 -0.155  -2.574
:FOR003: 3.ATOM   9.523  -7.118 -0.334  -6.318
:FOR003: 3.ATOM   8.574  -4.624 -0.479  -7.204

:FOR004: 4.ATOM  13.336 -10.788  0.424  -7.828
:FOR004: 4.ATOM  14.113 -11.064  0.465  -8.749
:FOR004: 4.ATOM   8.813 -7.202   0.214  -5.075
:FOR004: 4.ATOM   5.114  0.017   0.122  -5.113
:FOR004: 4.ATOM   6.266  1.913   0.081  -5.966
:FOR004: 4.ATOM   5.693  3.427   -0.043 -4.546