Local (111)-like reconstruction on highly-compressed Cu(001) regions

•Square c(2 × 2)N-adsorbed islands (5nm×5nm) aligned in [100] form grid-like nanopattern on Cu(001).•Short bright lines appear on edges of bare Cu(001) patches left at grid intersections.•Bright lines correspond to local (111)-like reconstruction, and relieve compressive strain.•Local (111)-like structure is formed by half-period shift of a Cu row in a [110] direction.•Shifted Cu row is terminated by missing-Cu-row structure of a narrow boundary between N-islands.