To verify whether the atomic positions are correct for a supercell containing four Ga and four As atoms, you can follow these steps:

1. Visualize the atomic positions: Plot the atomic positions in a visualization software or use the visualization capabilities of Quantum Espresso to check if they match your intended supercell structure. This will help you visually confirm the arrangement of Ga and As atoms in the cell.

2. Check the fractional coordinates: Ensure that the fractional coordinates of each atom fall within the range of 0 to 1, as they represent the fractional positions within the unit cell. The provided coordinates seem to be fractional coordinates, which is the correct format for Quantum Espresso input.

3. Verify the stoichiometry: Confirm that the atomic ratios of Ga and As in the supercell match your intended composition (in this case, four Ga and four As atoms). Count the number of Ga and As atoms listed in the atomic positions and make sure they align with your desired stoichiometry.

Once you have visually confirmed the atomic positions and verified the stoichiometry, you can proceed with performing calculations on your GaAs supercell using Quantum Espresso. Remember to set up the appropriate input parameters, such as pseudopotentials, exchange-correlation functionals, and k-points, as per your specific calculation requirements.

If you have any further questions or need assistance with the calculations, feel free to ask for guidance.