Fe5SiAs crystallizes in the monoclinic Cm space group. There are twenty inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted tetrahedral geometry to one Fe(19), one As(2), one As(3), and two equivalent As(4) atoms. In the second Fe site, Fe(2) is bonded in a 4-coordinate geometry to one Fe(13), two equivalent Fe(14), two equivalent Fe(18), two equivalent Si(1), one As(1), and one As(5) atom. In the third Fe site, Fe(3) is bonded in a 13-coordinate geometry to one Fe(11), one Fe(17), one Fe(7), two equivalent Fe(12), two equivalent Fe(15), two equivalent Fe(8), two equivalent Si(2), one As(1), and one As(3) atom. In the fourth Fe site, Fe(4) is bonded in a 13-coordinate geometry to one Fe(11), one Fe(18), one Fe(7), two equivalent Fe(12), two equivalent Fe(15), two equivalent Fe(8), two equivalent Si(2), one As(1), and one As(4) atom. In the fifth Fe site, Fe(5) is bonded in a 4-coordinate geometry to one Fe(13), one Fe(19), two equivalent Fe(14), two equivalent Fe(16), two equivalent Si(3), one As(2), and one As(5) atom. In the sixth Fe site, Fe(6) is bonded in a 13-coordinate geometry to one Fe(13), one Fe(20), one Fe(9), two equivalent Fe(10), two equivalent Fe(14), two equivalent Fe(16), one Si(1), two equivalent Si(3), and one As(2) atom. In the seventh Fe site, Fe(7) is bonded in a 4-coordinate geometry to one Fe(3), two equivalent Fe(18), two equivalent Fe(4), two equivalent Si(2), one As(1), and one As(5) atom. In the eighth Fe site, Fe(8) is bonded in a 4-coordinate geometry to one Fe(3), two equivalent Fe(18), two equivalent Fe(4), one Si(1), two equivalent Si(2), and one As(1) atom. In the ninth Fe site, Fe(9) is bonded in a 4-coordinate geometry to one Fe(13), one Fe(19), two equivalent Fe(6), two equivalent Si(3), one As(2), and one As(3) atom. In the tenth Fe site, Fe(10) is bonded in a 4-coordinate geometry to one Fe(14), one Fe(19), two equivalent Fe(6), two equivalent Si(3), one As(2), and one As(4) atom. In the eleventh Fe site, Fe(11) is bonded in a 3-coordinate geometry to one Fe(19), one Fe(3), two equivalent Fe(15), two equivalent Fe(4), one As(1), one As(3), and two equivalent As(4) atoms. In the twelfth Fe site, Fe(12) is bonded in a 3-coordinate geometry to one Fe(3), two equivalent Fe(15), two equivalent Fe(4), one As(1), one As(3), and two equivalent As(4) atoms. In the thirteenth Fe site, Fe(13) is bonded in a 12-coordinate geometry to one Fe(17), one Fe(2), one Fe(5), one Fe(9), two equivalent Fe(16), two equivalent Fe(6), two equivalent Si(1), one As(2), and one As(5) atom. In the fourteenth Fe site, Fe(14) is bonded in a 12-coordinate geometry to one Fe(10), one Fe(18), one Fe(2), one Fe(5), two equivalent Fe(16), two equivalent Fe(6), two equivalent Si(1), one As(2), and one As(5) atom. In the fifteenth Fe site, Fe(15) is bonded in a 10-coordinate geometry to one Fe(11), one Fe(3), two equivalent Fe(12), two equivalent Fe(4), one Si(2), one As(3), and two equivalent As(4) atoms. In the sixteenth Fe site, Fe(16) is bonded in a 10-coordinate geometry to one Fe(13), one Fe(5), two equivalent Fe(14), two equivalent Fe(6), one Si(3), two equivalent Si(1), and one As(5) atom. In the seventeenth Fe site, Fe(17) is bonded in a distorted single-bond geometry to one Fe(13), one Fe(3), two equivalent Si(1), two equivalent Si(2), and one As(5) atom. In the eighteenth Fe site, Fe(18) is bonded in a 11-coordinate geometry to one Fe(14), one Fe(2), one Fe(4), one Fe(7), two equivalent Fe(8), two equivalent Si(1), two equivalent Si(2), and one As(5) atom. In the nineteenth Fe site, Fe(19) is bonded in a 11-coordinate geometry to one Fe(1), one Fe(11), one Fe(5), one Fe(9), two equivalent Fe(10), two equivalent Si(3), one As(3), and two equivalent As(4) atoms. In the twentieth Fe site, Fe(20) is bonded in a 1-coordinate geometry to one Fe(6), two equivalent Si(3), one As(3), and two equivalent As(4) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to one Fe(13), one Fe(17), one Fe(2), one Fe(6), one Fe(8), two equivalent Fe(14), two equivalent Fe(16), and two equivalent Fe(18) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Fe(15), one Fe(17), one Fe(3), one Fe(7), two equivalent Fe(18), two equivalent Fe(4), and two equivalent Fe(8) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Fe(16), one Fe(19), one Fe(5), one Fe(9), two equivalent Fe(10), two equivalent Fe(20), and two equivalent Fe(6) atoms. There are five inequivalent As sites. In the first As site, As(1) is bonded in a 10-coordinate geometry to one Fe(11), one Fe(2), one Fe(3), one Fe(7), two equivalent Fe(12), two equivalent Fe(4), and two equivalent Fe(8) atoms. In the second As site, As(2) is bonded in a 10-coordinate geometry to one Fe(1), one Fe(13), one Fe(5), one Fe(9), two equivalent Fe(10), two equivalent Fe(14), and two equivalent Fe(6) atoms. In the third As site, As(3) is bonded in a 11-coordinate geometry to one Fe(1), one Fe(11), one Fe(19), one Fe(3), one Fe(9), two equivalent Fe(12), two equivalent Fe(15), and two equivalent Fe(20) atoms. In the fourth As site, As(4) is bonded in a 11-coordinate geometry to one Fe(1), one Fe(10), one Fe(11), one Fe(19), one Fe(4), two equivalent Fe(12), two equivalent Fe(15), and two equivalent Fe(20) atoms. In the fifth As site, As(5) is bonded in a 10-coordinate geometry to one Fe(13), one Fe(17), one Fe(2), one Fe(5), one Fe(7), two equivalent Fe(14), two equivalent Fe(16), and two equivalent Fe(18) atoms.
Fe5SiAs crystallizes in the monoclinic Cm space group. There are twenty inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted tetrahedral geometry to one Fe(19), one As(2), one As(3), and two equivalent As(4) atoms. The Fe(1)-Fe(19) bond length is 2.52 Å. The Fe(1)-As(2) bond length is 2.49 Å. The Fe(1)-As(3) bond length is 2.43 Å. Both Fe(1)-As(4) bond lengths are 2.44 Å. In the second Fe site, Fe(2) is bonded in a 4-coordinate geometry to one Fe(13), two equivalent Fe(14), two equivalent Fe(18), two equivalent Si(1), one As(1), and one As(5) atom. The Fe(2)-Fe(13) bond length is 2.75 Å. Both Fe(2)-Fe(14) bond lengths are 2.87 Å. Both Fe(2)-Fe(18) bond lengths are 2.52 Å. Both Fe(2)-Si(1) bond lengths are 2.40 Å. The Fe(2)-As(1) bond length is 2.48 Å. The Fe(2)-As(5) bond length is 2.42 Å. In the third Fe site, Fe(3) is bonded in a 13-coordinate geometry to one Fe(11), one Fe(17), one Fe(7), two equivalent Fe(12), two equivalent Fe(15), two equivalent Fe(8), two equivalent Si(2), one As(1), and one As(3) atom. The Fe(3)-Fe(11) bond length is 2.69 Å. The Fe(3)-Fe(17) bond length is 2.51 Å. The Fe(3)-Fe(7) bond length is 2.52 Å. Both Fe(3)-Fe(12) bond lengths are 2.58 Å. Both Fe(3)-Fe(15) bond lengths are 2.61 Å. Both Fe(3)-Fe(8) bond lengths are 2.73 Å. Both Fe(3)-Si(2) bond lengths are 2.39 Å. The Fe(3)-As(1) bond length is 2.58 Å. The Fe(3)-As(3) bond length is 2.51 Å. In the fourth Fe site, Fe(4) is bonded in a 13-coordinate geometry to one Fe(11), one Fe(18), one Fe(7), two equivalent Fe(12), two equivalent Fe(15), two equivalent Fe(8), two equivalent Si(2), one As(1), and one As(4) atom. The Fe(4)-Fe(11) bond length is 2.58 Å. The Fe(4)-Fe(18) bond length is 2.50 Å. The Fe(4)-Fe(7) bond length is 2.74 Å. There is one shorter (2.58 Å) and one longer (2.69 Å) Fe(4)-Fe(12) bond length. Both Fe(4)-Fe(15) bond lengths are 2.60 Å. There is one shorter (2.56 Å) and one longer (2.75 Å) Fe(4)-Fe(8) bond length. Both Fe(4)-Si(2) bond lengths are 2.39 Å. The Fe(4)-As(1) bond length is 2.57 Å. The Fe(4)-As(4) bond length is 2.50 Å. In the fifth Fe site, Fe(5) is bonded in a 4-coordinate geometry to one Fe(13), one Fe(19), two equivalent Fe(14), two equivalent Fe(16), two equivalent Si(3), one As(2), and one As(5) atom. The Fe(5)-Fe(13) bond length is 2.69 Å. The Fe(5)-Fe(19) bond length is 2.47 Å. Both Fe(5)-Fe(14) bond lengths are 2.63 Å. Both Fe(5)-Fe(16) bond lengths are 2.64 Å. Both Fe(5)-Si(3) bond lengths are 2.37 Å. The Fe(5)-As(2) bond length is 2.56 Å. The Fe(5)-As(5) bond length is 2.46 Å. In the sixth Fe site, Fe(6) is bonded in a 13-coordinate geometry to one Fe(13), one Fe(20), one Fe(9), two equivalent Fe(10), two equivalent Fe(14), two equivalent Fe(16), one Si(1), two equivalent Si(3), and one As(2) atom. The Fe(6)-Fe(13) bond length is 2.54 Å. The Fe(6)-Fe(20) bond length is 2.49 Å. The Fe(6)-Fe(9) bond length is 2.74 Å. There is one shorter (2.58 Å) and one longer (2.75 Å) Fe(6)-Fe(10) bond length. There is one shorter (2.53 Å) and one longer (2.62 Å) Fe(6)-Fe(14) bond length. Both Fe(6)-Fe(16) bond lengths are 2.65 Å. The Fe(6)-Si(1) bond length is 2.42 Å. Both Fe(6)-Si(3) bond lengths are 2.38 Å. The Fe(6)-As(2) bond length is 2.56 Å. In the seventh Fe site, Fe(7) is bonded in a 4-coordinate geometry to one Fe(3), two equivalent Fe(18), two equivalent Fe(4), two equivalent Si(2), one As(1), and one As(5) atom. Both Fe(7)-Fe(18) bond lengths are 2.64 Å. Both Fe(7)-Si(2) bond lengths are 2.36 Å. The Fe(7)-As(1) bond length is 2.34 Å. The Fe(7)-As(5) bond length is 2.37 Å. In the eighth Fe site, Fe(8) is bonded in a 4-coordinate geometry to one Fe(3), two equivalent Fe(18), two equivalent Fe(4), one Si(1), two equivalent Si(2), and one As(1) atom. There is one shorter (2.46 Å) and one longer (2.56 Å) Fe(8)-Fe(18) bond length. The Fe(8)-Si(1) bond length is 2.36 Å. Both Fe(8)-Si(2) bond lengths are 2.37 Å. The Fe(8)-As(1) bond length is 2.35 Å. In the ninth Fe site, Fe(9) is bonded in a 4-coordinate geometry to one Fe(13), one Fe(19), two equivalent Fe(6), two equivalent Si(3), one As(2), and one As(3) atom. The Fe(9)-Fe(13) bond length is 2.58 Å. The Fe(9)-Fe(19) bond length is 2.45 Å. Both Fe(9)-Si(3) bond lengths are 2.39 Å. The Fe(9)-As(2) bond length is 2.35 Å. The Fe(9)-As(3) bond length is 2.42 Å. In the tenth Fe site, Fe(10) is bonded in a 4-coordinate geometry to one Fe(14), one Fe(19), two equivalent Fe(6), two equivalent Si(3), one As(2), and one As(4) atom. The Fe(10)-Fe(14) bond length is 2.58 Å. The Fe(10)-Fe(19) bond length is 2.58 Å. There is one shorter (2.37 Å) and one longer (2.38 Å) Fe(10)-Si(3) bond length. The Fe(10)-As(2) bond length is 2.35 Å. The Fe(10)-As(4) bond length is 2.41 Å. In the eleventh Fe site, Fe(11) is bonded in a 3-coordinate geometry to one Fe(19), one Fe(3), two equivalent Fe(15), two equivalent Fe(4), one As(1), one As(3), and two equivalent As(4) atoms. The Fe(11)-Fe(19) bond length is 2.67 Å. Both Fe(11)-Fe(15) bond lengths are 2.50 Å. The Fe(11)-As(1) bond length is 2.54 Å. The Fe(11)-As(3) bond length is 2.92 Å. Both Fe(11)-As(4) bond lengths are 2.49 Å. In the twelfth Fe site, Fe(12) is bonded in a 3-coordinate geometry to one Fe(3), two equivalent Fe(15), two equivalent Fe(4), one As(1), one As(3), and two equivalent As(4) atoms. Both Fe(12)-Fe(15) bond lengths are 2.50 Å. The Fe(12)-As(1) bond length is 2.54 Å. The Fe(12)-As(3) bond length is 2.48 Å. There is one shorter (2.48 Å) and one longer (2.95 Å) Fe(12)-As(4) bond length. In the thirteenth Fe site, Fe(13) is bonded in a 12-coordinate geometry to one Fe(17), one Fe(2), one Fe(5), one Fe(9), two equivalent Fe(16), two equivalent Fe(6), two equivalent Si(1), one As(2), and one As(5) atom. The Fe(13)-Fe(17) bond length is 2.55 Å. Both Fe(13)-Fe(16) bond lengths are 2.52 Å. Both Fe(13)-Si(1) bond lengths are 2.46 Å. The Fe(13)-As(2) bond length is 2.51 Å. The Fe(13)-As(5) bond length is 3.00 Å. In the fourteenth Fe site, Fe(14) is bonded in a 12-coordinate geometry to one Fe(10), one Fe(18), one Fe(2), one Fe(5), two equivalent Fe(16), two equivalent Fe(6), two equivalent Si(1), one As(2), and one As(5) atom. The Fe(14)-Fe(18) bond length is 2.54 Å. There is one shorter (2.44 Å) and one longer (2.49 Å) Fe(14)-Fe(16) bond length. There is one shorter (2.47 Å) and one longer (2.85 Å) Fe(14)-Si(1) bond length. The Fe(14)-As(2) bond length is 2.58 Å. The Fe(14)-As(5) bond length is 2.50 Å. In the fifteenth Fe site, Fe(15) is bonded in a 10-coordinate geometry to one Fe(11), one Fe(3), two equivalent Fe(12), two equivalent Fe(4), one Si(2), one As(3), and two equivalent As(4) atoms. The Fe(15)-Si(2) bond length is 2.46 Å. The Fe(15)-As(3) bond length is 2.50 Å. There is one shorter (2.50 Å) and one longer (2.51 Å) Fe(15)-As(4) bond length. In the sixteenth Fe site, Fe(16) is bonded in a 10-coordinate geometry to one Fe(13), one Fe(5), two equivalent Fe(14), two equivalent Fe(6), one Si(3), two equivalent Si(1), and one As(5) atom. The Fe(16)-Si(3) bond length is 2.48 Å. There is one shorter (2.44 Å) and one longer (2.47 Å) Fe(16)-Si(1) bond length. The Fe(16)-As(5) bond length is 2.47 Å. In the seventeenth Fe site, Fe(17) is bonded in a distorted single-bond geometry to one Fe(13), one Fe(3), two equivalent Si(1), two equivalent Si(2), and one As(5) atom. Both Fe(17)-Si(1) bond lengths are 2.67 Å. Both Fe(17)-Si(2) bond lengths are 2.69 Å. The Fe(17)-As(5) bond length is 2.45 Å. In the eighteenth Fe site, Fe(18) is bonded in a 11-coordinate geometry to one Fe(14), one Fe(2), one Fe(4), one Fe(7), two equivalent Fe(8), two equivalent Si(1), two equivalent Si(2), and one As(5) atom. There is one shorter (2.43 Å) and one longer (2.62 Å) Fe(18)-Si(1) bond length. There is one shorter (2.60 Å) and one longer (2.68 Å) Fe(18)-Si(2) bond length. The Fe(18)-As(5) bond length is 2.73 Å. In the nineteenth Fe site, Fe(19) is bonded in a 11-coordinate geometry to one Fe(1), one Fe(11), one Fe(5), one Fe(9), two equivalent Fe(10), two equivalent Si(3), one As(3), and two equivalent As(4) atoms. Both Fe(19)-Si(3) bond lengths are 2.66 Å. The Fe(19)-As(3) bond length is 2.48 Å. Both Fe(19)-As(4) bond lengths are 2.73 Å. In the twentieth Fe site, Fe(20) is bonded in a 1-coordinate geometry to one Fe(6), two equivalent Si(3), one As(3), and two equivalent As(4) atoms. Both Fe(20)-Si(3) bond lengths are 2.66 Å. The Fe(20)-As(3) bond length is 2.73 Å. There is one shorter (2.46 Å) and one longer (2.75 Å) Fe(20)-As(4) bond length. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 11-coordinate geometry to one Fe(13), one Fe(17), one Fe(2), one Fe(6), one Fe(8), two equivalent Fe(14), two equivalent Fe(16), and two equivalent Fe(18) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to one Fe(15), one Fe(17), one Fe(3), one Fe(7), two equivalent Fe(18), two equivalent Fe(4), and two equivalent Fe(8) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Fe(16), one Fe(19), one Fe(5), one Fe(9), two equivalent Fe(10), two equivalent Fe(20), and two equivalent Fe(6) atoms. There are five inequivalent As sites. In the first As site, As(1) is bonded in a 10-coordinate geometry to one Fe(11), one Fe(2), one Fe(3), one Fe(7), two equivalent Fe(12), two equivalent Fe(4), and two equivalent Fe(8) atoms. In the second As site, As(2) is bonded in a 10-coordinate geometry to one Fe(1), one Fe(13), one Fe(5), one Fe(9), two equivalent Fe(10), two equivalent Fe(14), and two equivalent Fe(6) atoms. In the third As site, As(3) is bonded in a 11-coordinate geometry to one Fe(1), one Fe(11), one Fe(19), one Fe(3), one Fe(9), two equivalent Fe(12), two equivalent Fe(15), and two equivalent Fe(20) atoms. In the fourth As site, As(4) is bonded in a 11-coordinate geometry to one Fe(1), one Fe(10), one Fe(11), one Fe(19), one Fe(4), two equivalent Fe(12), two equivalent Fe(15), and two equivalent Fe(20) atoms. In the fifth As site, As(5) is bonded in a 10-coordinate geometry to one Fe(13), one Fe(17), one Fe(2), one Fe(5), one Fe(7), two equivalent Fe(14), two equivalent Fe(16), and two equivalent Fe(18) atoms.