[ESPResSo] Generalized Lennard-Jones Potential

[Lorenzo Isella]

Dear All,
I am trying to simulate a system interacting with a generalized 
Lennard-Jones(LJ) potential.
However, when I try running the simulation I get the following error 
message:

excessive parameter/unknown interaction type "lj-gen" in parsing non 
bonded interaction
   while executing
"inter 0 0 lj-gen $eps $sig $cut $shift $r_off $e1 $e2"

I think I should have enabled an extra feature in the configuration 
file, but looking at the part dealing with the interaction:

/**********************************************************************/
/*                           interactions                             */
/**********************************************************************/

#define TABULATED
#define LENNARD_JONES
#define SMOOTH_STEP
#define BMHTF_NACL
#define LJ_WARN_WHEN_CLOSE
#define MORSE
#define LJCOS
#define LJCOS2
#define BUCKINGHAM
#define SOFT_SPHERE

/* Note: Activate ONLY ONE bonded angle potential out of the following! */
/* #define BOND_ANGLE_HARMONIC */
#define BOND_ANGLE_COSINE
/* #define BOND_ANGLE_COSSQUARE */



it is hard for me to tell what went wrong...I enabled pretty much every 
sort of interaction, but I cannot see anything looking like a 
generalized LJ potential.
Am I missing the obvious?
Many thanks

Lorenzo Isella