# How to Include Parameters for Neutral Copper Atoms in GROMACS Force Field for MD Simulations? **URL:** \ **Category:** User discussions\ **Created:** [June 25, 2024, 1:13pm UTC](https://gromacs.bioexcel.eu/t/how-to-include-parameters-for-neutral-copper-atoms-in-gromacs-force-field-for-md-simulations/9510 "2024-06-25T13:13:21Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![aish.warya\_2024](https://avatars.discourse-cdn.com/v4/letter/a/b5ac83/32.png) [@aish.warya\_2024](https://gromacs.bioexcel.eu/u/aish.warya_2024)\ **Post date:** [June 25, 2024, 1:13pm UTC](https://gromacs.bioexcel.eu/t/how-to-include-parameters-for-neutral-copper-atoms-in-gromacs-force-field-for-md-simulations/9510/1 "2024-06-25T13:13:21Z")
GROMACS version: GROMACS modification: Yes/No Here post your question Dear GROMACS users, I need to perform MD simulations of Cu nanoparticles using GROMACS. I have created an `.itp` file for Cu with the following content: [moleculetype] ; Name nrexcl cu 1 [atoms] ; nr type resnr resid atom cgnr charge mass 1 CU 1 CU CU 1 2.0 63.546 ```auto However, I am encountering an error: `Atomtype CU not found`. The existing GROMACS `.itp` files only include data for Cu (+1) and Cu (+2) ions, not for the neutral Cu atom. Additionally, the `.itp` files are read-only, so I cannot add the data for neutral Cu. How can I resolve this issue? ``` ---
**Author:** ![Karis](https://avatars.discourse-cdn.com/v4/letter/k/ed8c4c/32.png) [@Karis](https://gromacs.bioexcel.eu/u/Karis)\ **Post date:** [June 26, 2024, 3:50pm UTC](https://gromacs.bioexcel.eu/t/how-to-include-parameters-for-neutral-copper-atoms-in-gromacs-force-field-for-md-simulations/9510/2 "2024-06-26T15:50:08Z")
Given that you’ve created a .itp file, you should be able to include the parameters in your topol.top with an #include command (you can refer to this [Protein-Ligand Complex](http://www.mdtutorials.com/gmx/complex/index.html) for an example). If you don’t have a starting topol.top, you can convert the .itp file into one by including whatever #include commands you need to call on your forcefield, or just generate one from a .pdb file you already know works and then replace the molecules in that file with the ones you actually want. ---
**Author:** ![aish.warya\_2024](https://avatars.discourse-cdn.com/v4/letter/a/b5ac83/32.png) [@aish.warya\_2024](https://gromacs.bioexcel.eu/u/aish.warya_2024)\ **Post date:** [June 27, 2024, 2:09pm UTC](https://gromacs.bioexcel.eu/t/how-to-include-parameters-for-neutral-copper-atoms-in-gromacs-force-field-for-md-simulations/9510/3 "2024-06-27T14:09:18Z")
Dear @Karis, I followed your instructions. Now its working. Thank you for ypur assistance