[gmx-users] Error:EM did not converge while using polarizable ion

[折晓会]

Dear all,

I am now trying to simulation polarizable LiCl solutions with Gromacs 5.0.5, where SWM4-NDP water model and corresponding polarizable ion model are used. The force field files come from professor Spoel and can be found in the website http://virtualchemistry.org/pol.php.

During the simulation, error occurs: 

step 63: EM did not converge in 100 iterations, RMS force 159.892
step 64: EM did not converge in 100 iterations, RMS force 542.311
step 65: EM did not converge in 100 iterations, RMS force 1064.542
step 66: EM did not converge in 100 iterations, RMS force 1168.229
step 67: EM did not converge in 100 iterations, RMS force 853.824
step 68: EM did not converge in 100 iterations, RMS force 842.719
step 69: EM did not converge in 100 iterations, RMS force 1211.043
step 70: EM did not converge in 100 iterations, RMS force 2015.682
step 71: EM did not converge in 100 iterations, RMS force 2926.036
step 72: EM did not converge in 100 iterations, RMS force 3314.541
step 73: EM did not converge in 100 iterations, RMS force 4813.701
step 74: EM did not converge in 100 iterations, RMS force 9258.925
step 76: EM did not converge in 100 iterations, RMS force 1761.227
step 77: EM did not converge in 100 iterations, RMS force 589.506
Segmentation fault (core dumped)

I also try to simulate the pure water with SWM4-NDP model, and it works well. I am wondering if anyone can help me. I failed to find answers on Google and am stuck here for a long time.

The force field for ions are as follows:

; Lithium, Li+
[ moleculetype ]
; molname    nrexcl
Li        1

[ atoms ]
; id    at type    res nr    residu name    at name    cg nr    charge
1    Lic    1    Li        Lic1    1     1.3104270
2    Lis    1    Li        Lis1    1    -0.3104270

[ polarization ]
; See notes above.    alpha (nm^3)
1    2    1     0.000032


; Chloride, Cl-
[ moleculetype ]
; molname    nrexcl
Cl        1

[ atoms ]
; id    at type    res nr    residu name    at name    cg nr    charge
1    Clc    1    Cl        Clc1    1     2.4571870
2    Cls    1    Cl        Cls1    1    -3.4571870

[ polarization ]
; See notes above.    alpha (nm^3)
1    2    1     0.003969


Any help will be appreciated!

Best wishes,

Xiaohui She
Ph.D. University of Wisconsin-Madison