# Standard library logic error (bug):?

**URL:** <https://gromacs.bioexcel.eu/t/standard-library-logic-error-bug/11599>\
**Category:** User discussions\
**Created:** [February 20, 2025, 11:02am UTC](https://gromacs.bioexcel.eu/t/standard-library-logic-error-bug/11599 "2025-02-20T11:02:04Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![mj.rezayani](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/mj.rezayani/32/3918_2.png) [@mj.rezayani](https://gromacs.bioexcel.eu/u/mj.rezayani)\
**Post date:** [February 20, 2025, 11:02am UTC](https://gromacs.bioexcel.eu/t/standard-library-logic-error-bug/11599/1 "2025-02-20T11:02:04Z")

</div>

Dear GMX users,

I want to study the diffusion of methanol in MFI Zeolite. I want to study the ballistic motion then I have to save the trajectory of Methanol at a very small number of steps (e.g., nstxout = 200).

However, when I want to plot the MSD using gmx MSD for (nstxout = 200 ) for a 50 ps NVT run , it shows this error:

```auto
Standard library logic error (bug):
(exception type: St12length_error)
vector::_M_default_append

```

This error exists till nstxout = 5000. After 5000 the msd is plotted without any error. Could you please tell me what the problem is?  
gmx version is: 2022  
[nvt.mdp|attachment]

I have attached the nvt.mdp file here.

[nvt.mdp](https://gromacs.bioexcel.eu/uploads/short-url/33JznHwOOvNevfQwExOq1VMOoNh.mdp) (2.4 KB)