问题背景：fdpna3单晶结构如图
这里用到的fdp3-离子是从单晶结构中抠出的；原子电荷和itp,top,gro文件是高斯+multiwfn+sobtop得到的。
1.在em的过程中总是出现成键异常问题，优化结束后总是有如下Energy minimization has stopped, but the forces have not converged to the
requested precision Fmax < 200 (which may not be possible for your system).
It stopped because the algorithm tried to make a new step whose size was too
small, or there was no change in the energy since last step. Either way, we
regard the minimization as converged to within the available machine
precision, given your starting configuration and EM parameters.
Double precision normally gives you higher accuracy, but this is often not
needed for preparing to run molecular dynamics.
You might need to increase your constraint accuracy, or turn
off constraints altogether (set constraints = none in mdp file)
writing lowest energy coordinates.
Steepest Descents converged to machine precision in 68 steps,
but did not reach the requested Fmax < 200.
Potential Energy = -2.2743614e+05
Maximum force = 1.1228680e+05 on atom 34
Norm of force = 1.3950730e+03