def find_vasprun_files():
    folders = glob.glob('split-*')
    folders = sorted(folders) if folders else ['.']
    filenames = []
    for fol in folders:
        vr_file = os.path.join(fol, 'vasprun.xml')
        vr_file_gz = os.path.join(fol, 'vasprun.xml.gz')
        if os.path.exists(vr_file):
            filenames.append(vr_file)
        elif os.path.exists(vr_file_gz):
            filenames.append(vr_file_gz)
        else:
            logging.error('ERROR: No vasprun.xml found in {}!'.format(fol))
            sys.exit()
    return filenames