Sajida Laraib The script you provided seems to be a PBS job script for running VASP (Vienna Ab initio Simulation Package) on a computing cluster. However, the issue you mentioned with the CONTCAR file being 0kb could be due to several reasons. Here are a few potential causes and suggestions to address the problem:

1. Verify the File Path: Double-check that the script is running in the correct working directory where the CONTCAR file should be generated. Make sure the path to the CONTCAR file is correctly specified in the VASP input files.

2. Check VASP Input Files: Ensure that the input files required by VASP (e.g., INCAR, POSCAR) are present and properly formatted. Verify that the POSCAR file contains the correct atomic positions and the necessary information for the simulation.

3. Confirm VASP Execution: Check if the VASP executable (`vasp_std`) is correctly installed in the specified path `/opt/software/vasp/vasp.5.4.1/bin/`. Ensure that the version of VASP you are using is compatible with your system.

4. Review PBS Job Configuration: Make sure the PBS job configuration (PBS directives) are appropriate for your computing environment. Verify that the requested number of nodes, processors per node, and walltime are correctly set according to your cluster's specifications.

5. Debugging Output: Modify the script to redirect the output and error messages to a file. This way, you can examine any error messages or warnings that may help diagnose the problem. You can add the following lines to your script:

```bash

mpirun -genv I_MPI_DEVICE ssm -machinefile /tmp/nodefile.$$ -n $NP $EXEC -s -deffnm em -v > output.log 2>&1

```

This will redirect both standard output and standard error to the `output.log` file, allowing you to investigate any potential issues.

6. Seek System Administrator Support: If the above steps do not resolve the issue, it might be beneficial to reach out to the system administrators of your computing cluster. They can provide insights specific to your cluster's configuration and help troubleshoot the problem further.

Remember to adapt the suggestions based on your specific requirements and the configuration of your computing environment.