# Warning Atom Type Previously Defined Inquiry? **URL:** \ **Category:** User discussions\ **Created:** [August 27, 2020, 12:32pm UTC](https://gromacs.bioexcel.eu/t/warning-atom-type-previously-defined-inquiry/718 "2020-08-27T12:32:24Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![mjsubach](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/mjsubach/32/387_2.png) [@mjsubach](https://gromacs.bioexcel.eu/u/mjsubach)\ **Post date:** [August 27, 2020, 12:32pm UTC](https://gromacs.bioexcel.eu/t/warning-atom-type-previously-defined-inquiry/718/1 "2020-08-27T12:32:24Z")
Hello I am working through Gromacs Tutorial 2 (Membrane) and received several warnings upon inputting the below command: gmx grompp -f minim.mdp -c dppc128.pdb -p topol\_dppc.top -o dppc.tpr 12 warnings (12:12 posted below): WARNING 12 [file ffbonded.itp, line 556]: Atomtype LC2 was defined previously (e.g. in the forcefield files), and has now been defined again. This could happen e.g. if you would use a self-contained molecule .itp file that duplicates or replaces the contents of the standard force-field files. You should check the contents of your files and remove such repetition. If you know you should override the previous definition, then you could choose to suppress this warning with -maxwarn. and a 13th warning below: WARNING 13 [file topol\_dppc.top, line 26]: The GROMOS force fields have been parametrized with a physically incorrect multiple-time-stepping scheme for a twin-range cut-off. When used with a single-range cut-off (or a correct Trotter multiple-time-stepping scheme), physical properties, such as the density, might differ from the intended values. Since there are researchers actively working on validating GROMOS with modern integrators we have not yet removed the GROMOS force fields, but you should be aware of these issues and check if molecules in your system are affected before proceeding. Further information is available at [https://redmine.gromacs.org/issues/2884](https://redmine.gromacs.org/issues/2884) , and a longer explanation of our decision to remove physically incorrect algorithms can be found at [https://doi.org/10.26434/chemrxiv.11474583.v1](https://doi.org/10.26434/chemrxiv.11474583.v1) . May I Maxwarn/Disregards all? Much Thanks:) Joel ---
**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\ **Post date:** [August 27, 2020, 4:49pm UTC](https://gromacs.bioexcel.eu/t/warning-atom-type-previously-defined-inquiry/718/2 "2020-08-27T16:49:56Z")
Warning 12 means you haven’t constructed the force field files appropriately. Warning 13 can be overridden with `-maxwarn` for the purpose of completing the tutorial but should not be a general habit. There may be concerns about reproducibility with GROMOS simulations for the reasons discussed in the linked information. ---
**Author:** ![mjsubach](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/mjsubach/32/387_2.png) [@mjsubach](https://gromacs.bioexcel.eu/u/mjsubach)\ **Post date:** [August 27, 2020, 5:46pm UTC](https://gromacs.bioexcel.eu/t/warning-atom-type-previously-defined-inquiry/718/3 "2020-08-27T17:46:56Z")
Hello and thank you for your kind update, success:) Much Thanks:)