# FEL slow growth versus Fast growth TI

**URL:** <https://gromacs.bioexcel.eu/t/fel-slow-growth-versus-fast-growth-ti/3384>\
**Category:** User discussions\
**Tags:** analysis-tools\
**Created:** [December 30, 2021, 2:35pm UTC](https://gromacs.bioexcel.eu/t/fel-slow-growth-versus-fast-growth-ti/3384 "2021-12-30T14:35:57Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![alexmathew](https://avatars.discourse-cdn.com/v4/letter/a/f4b2a3/32.png) [@alexmathew](https://gromacs.bioexcel.eu/u/alexmathew)\
**Post date:** [December 30, 2021, 2:35pm UTC](https://gromacs.bioexcel.eu/t/fel-slow-growth-versus-fast-growth-ti/3384/1 "2021-12-30T14:35:57Z")

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GROMACS version:  
GROMACS modification: Yes/No  
Here post your question  
Dear All,  
I would like to know which method is more accurate for FEP calculations (Slow growth versus Fast growth TI). Further, I intend to obtain Free energy of single amino acid mutations using the following MDP parameters (modified MDP from Justin tutorial). Do i need to make mass lamda here? for a single point muation?

; init\_lambda\_state 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20  
vdw\_lambdas = 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00  
coul\_lambdas = 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00  
bonded\_lambdas = 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00  
restraint\_lambdas = 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00  
mass\_lambdas = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00  
temperature\_lambdas = 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00