Everything you wanted to know about gromacs but were affraid to ask: In energy minimization output file the energy for some steps is missing e.g.: Step Time Lambda Annealing 33 33.00000 0.00000 0.00000 Step Time Lambda Annealing 34 34.00000 0.00000 0.00000 What does it mean ? Thank you Vojtech Spiwok ICT Prague