"n" in the file name represents the order of the Ruddlesden-Popper (RP) phase nickelates 
with a general formula R_{n+1}Ni_{n}O_{3n+1}

n_3 has the data for the structure: n = 3 La4Ni3O10 nickelate
n_4 has the data for the structure: n = 4 La5Ni4O13 nickelate
n_5 has the data for the structure: n = 5 La6Ni5O16 nickelate
n_6 has the data for the structure: n = 6 La7Ni6O19 nickelate
LaNiO3 has the data for the perovskite structure: n = \infty LaNiO3 nickelate