Calculate long-range electrostatic interaction using Reaction Field

GROMACS version: 2018
GROMACS modification: No

Dear all,
I have performed a Steer molecular dynamics simulation, in which I fixed molecule A (named Rib in my system) and pull molecule B (Nascent in my system) away.
During the simulation, I used the PME method for long-range electrostatics, now I want to calculate electrostatic interaction between molecule A and B (both long-range and short-range so I used Reaction Field to obtain long-range interaction as this paper mention: https://pubs.acs.org/doi/abs/10.1021/acs.jcim.5b00012)

In the mdp file for interaction energy calculation:

energygrps = Rib Nascent
coulombtype = Reaction-Field
rcoulomb = 1.2

This means that the interaction of atoms in molecules Rib and molecule Nascent will be treated as short-range interaction if the distance smaller than 1.2 nm, and long-range if larger than 1.2 nm.

When I use gmx energy to calculate interaction energy I got only these options:

  1  Bond             2  Angle            3  Proper-Dih.      4  Improper-Dih. 
  5  LJ-14            6  Coulomb-14       7  LJ-(SR)          8  Disper.-corr. 
  9  Coulomb-(SR)    10  Position-Rest.  11  COM-Pull-En.    12  Potential     
 13  Kinetic-En.     14  Total-Energy    15  Conserved-En.   16  Temperature   
 17  Pres.-DC        18  Pressure        19  Constr.-rmsd    20  Vir-XX        
 21  Vir-XY          22  Vir-XZ          23  Vir-YX          24  Vir-YY        
 25  Vir-YZ          26  Vir-ZX          27  Vir-ZY          28  Vir-ZZ        
 29  Pres-XX         30  Pres-XY         31  Pres-XZ         32  Pres-YX       
 33  Pres-YY         34  Pres-YZ         35  Pres-ZX         36  Pres-ZY       
 37  Pres-ZZ                             38  #Surf*SurfTen                     
 39  Coul-SR:Rib-Rib                     40  LJ-SR:Rib-Rib                     
 41  Coul-14:Rib-Rib                     42  LJ-14:Rib-Rib                     
 43  Coul-SR:Rib-Nascent                 44  LJ-SR:Rib-Nascent                 
 45  Coul-14:Rib-Nascent                 46  LJ-14:Rib-Nascent                 
 47  Coul-SR:Rib-rest                    48  LJ-SR:Rib-rest                    
 49  Coul-14:Rib-rest                    50  LJ-14:Rib-rest                    
 51  Coul-SR:Nascent-Nascent             52  LJ-SR:Nascent-Nascent             
 53  Coul-14:Nascent-Nascent             54  LJ-14:Nascent-Nascent             
 55  Coul-SR:Nascent-rest                56  LJ-SR:Nascent-rest                
 57  Coul-14:Nascent-rest                58  LJ-14:Nascent-rest                
 59  Coul-SR:rest-rest                   60  LJ-SR:rest-rest                   
 61  Coul-14:rest-rest                   62  LJ-14:rest-rest                   
 63  T-RNC                               64  T-Water_and_ions     

How can I obtain the long-range electrostatic interactions?
Best regards,

energygrps can only decompose short-range nonbonded forces.

Dear Justin,
So how can I get the long-range electrostatic interactions?
Best regards,
Quyen

I don’t know of a way to calculate those energies.

Thanks, Justin