NaEuAsS4 crystallizes in the orthorhombic Ama2 space group. Na(1) is bonded to one S(3), two equivalent S(1), and two equivalent S(2) atoms to form distorted NaS5 trigonal bipyramids that share  a cornercorner with one As(1)S4 tetrahedra, corners with two equivalent Na(1)S5 trigonal bipyramids, and edges with two equivalent As(1)S4 tetrahedra. Eu(1) is bonded in a 8-coordinate geometry to two equivalent S(2), two equivalent S(3), and four equivalent S(1) atoms. As(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form AsS4 tetrahedra that share  a cornercorner with one Na(1)S5 trigonal bipyramid and edges with two equivalent Na(1)S5 trigonal bipyramids. There are three inequivalent S sites. In the first S site, S(1) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Eu(1), and one As(1) atom. In the second S site, S(2) is bonded to two equivalent Na(1), two equivalent Eu(1), and one As(1) atom to form distorted SNa2Eu2As trigonal bipyramids that share corners with four equivalent S(2)Na2Eu2As trigonal bipyramids, corners with three equivalent S(3)NaEu2As trigonal pyramids, and edges with two equivalent S(3)NaEu2As trigonal pyramids. In the third S site, S(3) is bonded to one Na(1), two equivalent Eu(1), and one As(1) atom to form SNaEu2As trigonal pyramids that share corners with three equivalent S(2)Na2Eu2As trigonal bipyramids, corners with two equivalent S(3)NaEu2As trigonal pyramids, and edges with two equivalent S(2)Na2Eu2As trigonal bipyramids.
NaEuAsS4 crystallizes in the orthorhombic Ama2 space group. Na(1) is bonded to one S(3), two equivalent S(1), and two equivalent S(2) atoms to form distorted NaS5 trigonal bipyramids that share  a cornercorner with one As(1)S4 tetrahedra, corners with two equivalent Na(1)S5 trigonal bipyramids, and edges with two equivalent As(1)S4 tetrahedra. The Na(1)-S(3) bond length is 2.75 Å. Both Na(1)-S(1) bond lengths are 2.88 Å. There is one shorter (2.89 Å) and one longer (3.20 Å) Na(1)-S(2) bond length. Eu(1) is bonded in a 8-coordinate geometry to two equivalent S(2), two equivalent S(3), and four equivalent S(1) atoms. Both Eu(1)-S(2) bond lengths are 3.04 Å. Both Eu(1)-S(3) bond lengths are 2.92 Å. There are two shorter (3.12 Å) and two longer (3.27 Å) Eu(1)-S(1) bond lengths. As(1) is bonded to one S(2), one S(3), and two equivalent S(1) atoms to form AsS4 tetrahedra that share  a cornercorner with one Na(1)S5 trigonal bipyramid and edges with two equivalent Na(1)S5 trigonal bipyramids. The As(1)-S(2) bond length is 2.24 Å. The As(1)-S(3) bond length is 2.22 Å. Both As(1)-S(1) bond lengths are 2.21 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded in a 4-coordinate geometry to one Na(1), two equivalent Eu(1), and one As(1) atom. In the second S site, S(2) is bonded to two equivalent Na(1), two equivalent Eu(1), and one As(1) atom to form distorted SNa2Eu2As trigonal bipyramids that share corners with four equivalent S(2)Na2Eu2As trigonal bipyramids, corners with three equivalent S(3)NaEu2As trigonal pyramids, and edges with two equivalent S(3)NaEu2As trigonal pyramids. In the third S site, S(3) is bonded to one Na(1), two equivalent Eu(1), and one As(1) atom to form SNaEu2As trigonal pyramids that share corners with three equivalent S(2)Na2Eu2As trigonal bipyramids, corners with two equivalent S(3)NaEu2As trigonal pyramids, and edges with two equivalent S(2)Na2Eu2As trigonal bipyramids.