Hi Amrita,
Please always reply-all so this thread goes to the mailing list, thanks.
Since your structure is Zn and O, your pair_coeff should be 3 2, not 2 3. Reax and reax/c doc pages have detailed descriptions.
With the change and the new data file I am not seeing “hbond” error messages anymore, but I still see nan. If you visualize your snapshot, you can see you have atoms that are too close to each other. You have a bad structure, most likely a bad boundary condition. Fix the boundary condition then I am sure you can run this.
Best,
Ray