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The new quaternary thiosilicate, Li2PbSiS4 (dilithium lead silicon tetrasulfide), was prepared in an evacuated fused‐silica tube via high‐temperature, solid‐state synthesis at 800 °C, followed by slow cooling. The crystal structure was solved and refined using single‐crystal X‐ray diffraction data. By strict definition, the title compound crystallizes in the stannite structure type; however, this type of structure can also be described as a compressed chalcopyrite‐like structure. The Li+ cation lies on a crystallographic fourfold rotoinversion axis, while the Pb2+ and Si4+ cations reside at the intersection of the fourfold rotoinversion axis with a twofold axis and a mirror plane. The Li+ and Si4+ cations in this structure are tetrahedrally coordinated, while the larger Pb2+ cation adopts a distorted eight‐coordinate dodecahedral coordination. These units join together via corner‐ and edge‐sharing to create a dense, three‐dimensional structure. Powder X‐ray diffraction indicates that the title compound is the major phase of the reaction product. Electronic structure calculations, performed using the full potential linearized augmented plane wave method within density functional theory (DFT), indicate that Li2PbSiS4 is a semiconductor with an indirect bandgap of 2.22 eV, which compares well with the measured optical bandgap of 2.51 eV. The noncentrosymmetric crystal structure and relatively wide bandgap designate this compound to be of interest for IR nonlinear optics. [ABSTRACT FROM AUTHOR]

The quaternary thio­germanates Cu4FeGe2S7 (tetra­copper iron digermanium hepta­sulfide) and Cu4CoGe2S7 (tetra­copper cobalt digermanium hepta­sulfide) were prepared in evacuated fused-silica ampoules via high-temperature, solid-state synthesis using stoichiometric amounts of the elements at 1273 K. These isostructural compounds crystallize in the Cu4NiSi2S7 structure type, which can be considered as a superstructure of cubic diamond or sphalerite. The monovalent (Cu+), divalent (Fe2+ or Co2+) and tetra­valent (Ge4+) cations adopt tetra­hedral geometries, each being surrounded by four S2− anions. The divalent cation and one of the sulfide ions lie on crystallographic twofold axes. These tetra­hedra share corners to create a three-dimensional framework structure. All of the tetra­hedra align along the same crystallographic direction, rendering the structure non-centrosymmetric and polar (space group C2). Analysis of X-ray powder diffraction data revealed that the structures are the major phase of the reaction products. Thermal analysis indicated relatively high melting temperatures, near 1273 K. [ABSTRACT FROM AUTHOR]

Abstract The series of quaternary rare-earth phosphides RE MnCuP 2 (RE = Y, La–Nd, Sm, Gd–Tm, Lu), which had previously been limited to the Yb member, has been prepared by reaction of the elements at 800 °C. These phosphides adopt the CaAl 2 Si 2 -type structure (trigonal, space group P 3 ¯ m 1 , Z = 1) with Mn and Cu atoms disordered over the tetrahedral M sites within [ M 2 P 2 ] slabs. However, single-crystal X-ray diffraction studies, carried out on some of these members (RE = Tb, Dy, Er, Tm), provide evidence for an interstitial octahedral site being partially occupied by Cu atoms, resulting in the nonstoichiometric formulation RE MnCu 1+ x P 2 (x = 0.10–0.16). A second polymorph of LaMnCuP 2 adopting the BaCu 2 S 2 -type structure (orthorhombic, space group Pnma , Z = 4) was also identified in the course of these investigations. Electronic structure calculations on a ordered superstructure model of YMnCuP 2 indicate the absence of a band gap. Graphical abstract RE MnCuP 2 with CaAl 2 Si 2 -type structure forms for nearly all RE members, and LaMnCuP 2 forms an additional BaCu 2 S 2 -type polymorph. fx1 Highlights • Phosphides RE MnCuP 2 with CaAl 2 Si 2 -type structure were prepared for nearly all RE. • Slight excess of Cu atoms can be accommodated in interstitial octahedral sites. • LaMnCuP 2 forms a second polymorph with BaCu 2 S 2 -type structure. • Calculations on YMnCuP 2 indicate absence of band gap. [ABSTRACT FROM AUTHOR]

The four ternary arsenides ATt 3 As 3 ( A =K, Rb; Tt =Ge, Sn) were obtained by reaction of the elements at 600–650 °C. They adopt an orthorhombic structure (space group Pnma , Z =4, with cell parameters ranging from a =9.9931(11) Å, b =3.7664(4) Å, c =18.607(2) Å for KGe 3 As 3 to a =10.3211(11) Å, b =4.0917(4) Å, c =19.570(2) Å for RbSn 3 As 3 ) containing corrugated [ Tt 3 As 3 ] layers built from Tt -centred trigonal pyramids and tetrahedra forming five-membered rings decorated with As handles. They can be considered to be Zintl phases with Tt atoms in +4, +3, and +1 oxidation states. Band structure calculations predict that these compounds are semiconductors with narrow band gaps (0.71 eV in KGe 3 As 3 , 0.50 eV in KSn 3 As 3 ). [ABSTRACT FROM AUTHOR]

The formation of quaternary rare-earth (RE) germanides containing transition metals (M's) from groups 6 to 10 was investigated through arc-melting and annealing reactions at 800 °C; about 50 new compounds were obtained. These include several new series of quaternary germanides RE4M2InGe4 (M = Fe, Co, Ru, Rh, Ir), previously known only for M = Mn and Ni; additional members of RE4Ni2InGe4 extended to other RE substituents; and a different but closely related series RE4RhInGe4. Detailed crystal structures were determined by single-crystal X-ray diffraction studies for 20 compounds. Monoclinic structures in space group C2/m are adopted by RE4M2InGe4 (Ho4Ni2InGe4-type, a = 15.1-16.5 Å, b = 4.1-4.4 Å, c = 6.9-7.3 Å, β = 106.2-108.6°) and RE4RhInGe4 (own type, a = 20.0-20.2 Å, b = 4.2-4.3 Å, c = 10.1-10.2 Å, β = 105.0-105.3°). Both structures contain frameworks built from MGe4 tetrahedra, InGe4 square planes, and Ge2 dimers, delimiting tunnels occupied by RE atoms. These structures can also be derived by cutting slabs along different directions from the more symmetrical RE2InGe2 structure. Although the Ge2 dimers are relatively invariant, the InGe4 square planes can undergo distortion to form two sets of short versus long In-Ge distances. This distortion results from a competition between M-Ge bonding in the MGe4 tetrahedra and In-Ge bonding in the InGe4 square planes. [ABSTRACT FROM AUTHOR]

The quaternary rare-earth phosphides REMnCu4P3 (RE = Gd-Ho) were obtained from direct reactions of the elements at 800 °C. They are the first examples in which ordering of two different transition-metal atoms takes place within the orthorhombic YCo5P3-type structure [Pearson symbol oP36, space group Pnma, Z = 4; a = 12.667(2)-12.6489(4) Å, b = 3.8119(7)-3.7755(1) Å, and c = 10.895(2)-10.8632(4) Å for RE = Gd-Ho]. Columns of trigonal prisms centered by P atoms are connected in propellor-shaped units in zigzag arrangements to generate square-pyramidal (CN5) sites that are occupied by Mn atoms and tetrahedral sites (CN4) that are occupied by Cu atoms. Spin-polarized band-structure calculations predict that the hypothetical compound YMnCu4P3 will exhibit magnetic ordering. Electrical resistivity measurements on TbMnCu4P3 indicate a poor metal. [ABSTRACT FROM AUTHOR]

Reactions of the elements at high temperature resulted in the quaternary arsenides KCdGeAs2 (650 °C) and RbCdGeAs2 (600 °C). Single-crystal X-ray diffraction analysis reveals that they adopt a new triclinic structure type (space group P1, Pearson symbol aP20, Z = 4; a = 8.0040(18) Å, b = 8.4023(19) Å, c = 8.703(2) Å, α = 71.019(3)°, β = 75.257(3)°, γ = 73.746(3)° for KCdGeAs2; a = 8.2692(13) Å, b = 8.4519(13) Å, c = 8.7349(13) Å, α = 71.163(2)°, β = 75.601(2)°, γ = 73.673(2)° for RbCdGeAs2). Two-dimensional anionic layers [CdGeAs2]- are separated by A+ cations and are built from ethane-like Ge2As6 units forming infinite chains connected via three- and four-coordinated Cd atoms. Being Zintl phases, these compounds satisfy charge balance and are expected to be semiconducting, as confirmed by band structure calculations on KCdGeAs2, which reveal a band gap of 0.8 eV. KCdGeAs2 is diamagnetic. [ABSTRACT FROM AUTHOR]

Abstract: Three series of quaternary rare-earth transition-metal pnictides REMM′Pn 2 (M=Cu, Ag; M′=Zn; Pn=P, As) have been prepared by reaction of the elements at 800°C, with crystal growth promoted through the addition of iodine. The extent of RE substitution is broad in these series: RECuZnAs2 (RE=Y, La Nd, Sm, Gd–Lu), REAgZnP2 (RE=La–Nd, Sm, Gd–Dy), and REAgZnAs2 (RE=La Nd, Sm, Gd Dy). Powder and single-crystal X-ray diffraction analysis revealed that they adopt the trigonal CaAl2Si2-type structure (space group P m1, Z=1), in which Cu or Ag atoms are disordered with Zn atoms over the unique tetrahedrally coordinated transition-metal site. Magnetic measurements indicated Curie–Weiss behavior for several members of the RECuZnAs2 and REAgZnP2 series. Core-line X-ray photoelectron spectra (XPS) collected on some RECuZnAs2 members corroborate the charge assignment deduced by the Zintl concept for these compounds, (RE 3+)(M 1+)(Zn2+)(Pn 3−)2. Optical diffuse reflectance spectra and valence band XPS spectra established that these compounds are small band-gap semiconductors (up to ~0.8eV in REAgZnP2) or semimetals (RECuZnAs2). Band structure calculations also support this electronic structure and indicate that the band gap can be narrowed through appropriate chemical substitution (RE=smaller atoms, M=Cu, and Pn=As). [Copyright &y& Elsevier]

Six series of quaternary rare-earth transition-metal chalcogenides RE 3 MGaCh 7 (M=Fe, Co, Ni; Ch=S, Se), comprising 33 compounds in total, have been prepared by reactions of the elements at 1050°C (for the sulphides) or 900°C (for the selenides). They adopt noncentrosymmetric hexagonal structures (ordered Ce3Al1.67S7-type, space group P63, Z=2) with cell parameters in the ranges of a=9.5–10.2Å and c=6.0–6.1Å for the sulphides and a=10.0–10.5Å and c=6.3–6.4Å for the selenides as refined from powder X-ray diffraction data. Single-crystal structures were determined for five members of the sulphide series RE 3FeGaS7 (RE=La, Pr, Tb) and RE 3CoGaS7 (RE=La, Tb). The highly anisotropic crystal structures consist of one-dimensional chains of M-centred face-sharing octahedra and stacks of Ga-centred tetrahedra all pointing in the same direction. Magnetic measurements on the sulphides reveal paramagnetic behaviour in some cases and long-range antiferromagnetic behaviour with low Néel temperatures (15K or lower) in others. Ga L-edge XANES spectra support the presence of highly cationic Ga tetrahedral centres with a tendency towards more covalent Ga–Ch character on proceeding from the sulphides to the selenides. Band structure calculations on La3FeGaS7 indicate that the electronic structure is dominated by Fe 3d-based states near the Fermi level. [ABSTRACT FROM AUTHOR]

Six quaternary rare-earth-containing sulphides RE 3 MInS7 (M=Fe, Co, Ni) have been prepared by reactions of the elements at 1050–1150°C. They are the first examples of chalcogenides RE 3 MM'Ch 7 adopting related La3CuSiS7- or ordered Ce3Al1.67S7-type structures in which the M' component is indium. They crystallize in the noncentrosymmetric hexagonal space group P63 with Z=2 and cell parameters in the ranges of a=9.95–10.15Å and c=6.25–6.29Å for RE 3FeInS7 (RE=La–Pr), RE 3CoInS7 (RE=La, Ce), and La3NiInS7. The crystal structure consists of parallel chains of face-sharing M-centred octahedra and stacks of In-centred tetrahedra, all pointing in the same polar direction, with seven-coordinate La atoms in the intervening spaces. X-ray photoelectron spectra support the valence assignments implied by the formulation (RE 3+)3(M 2+)(In3+)(S2−)7. Magnetic measurements are suggestive of antiferromagnetic coupling between the M moments. Band structure calculations reveal that a band gap of 0.25eV is present in La3FeInS7, whereas the increased electron count in La3CoInS7 and La3NiInS7 causes the Fermi level to cut narrow bands. [ABSTRACT FROM AUTHOR]

The ternary pnictides Rb4Zn7As7 and Rb7Mn12Sb12 and their quaternary derivatives Rb4Mn35Zn3 5Sb, and Rb7Mn4CdRSb12 have been prepared by reactions of the elements at 600 °C. They crystallize in two new structure types: orthorhombic Rb4Zn7As7-type (space group Cm cm, Z = 4; a = 4.1883(4) A, b = 24.844(2) A, c = 17.6056(17) À for Rb4Zn7As7 a = 4.3911(8) À, b = 26.546(5) A, c = 18.743(4) A for Rb4Mn35Zn3 5Sb7 and monoclinic Rb7Mnl2Sb12-type (space group C2/m, Z = 2; a = 26.544(12) A, b = 4.448(2) A, c = 16.676(8) A, ß = 103.183(8)° for RbMn12Sb12 a = 27.009(4) A, b = 4.5752(7) A, c = 16.727(3) A, ß = 103.221(2)° for Rb7Mn4Cd8Sb12). These related structures contain corrugated anionic layers built up by connecting ribbons of edge-sharing tetrahedra in a zigzag-like manner with chains of Mn-centered square pyramids located at the hinges. Homoatomic pnicogen--pnicogen bonding occurs in die form of Pn2 pairs. The compounds are formally deficient by one electron per formula unit, as confirmed by band structure calculations which reveal the location of the Fermi level just below a small gap in Rb4Zn7As7 or a pseudogap in Rb7Mn12Sb12. [ABSTRACT FROM AUTHOR]

The quaternary germanides RE4Mn2InGe4 (RE = La-Nd, Sm, Gd-Tm, Lu) have been prepared by arc-melting reactions of the elements and annealing at 800°C and represent the second example of the RE4M2InGe4 series previously known only for M = Ni. Single-crystal X-ray diffraction studies conducted on the earlier RE members of RE4Mn2InGe4 confirmed that they adopt the monoclinic Ho4Ni2InGe4-type structure [space group C2/m, a = 16.646(2)-15.9808(9) Å, b = 4.4190(6)-4.2363(2) Å, c = 7.4834(10)--7.1590(4) Å, β = 106.893(2)-106.304(1)° in the progression of RE from La to Gd]. The covalent framework contains Mn-centered tetrahedra and Ge2 dimers that build up [Mn2Ge4] layers, which are held weakly together by four-coordinate In atoms and outline tunnels filled by the RE atoms. This bonding picture is supported by band-structure calculations. An alternative description based on Ge-centered trigonal prisms reveals that RE4Mn2InGe4 is closely related to RE2InGe2. The electrical resistivity behavior of Pr4Mn2InGe4 is similar to that of Pr2InGe2. [ABSTRACT FROM AUTHOR]

Through arc-melting reactions of the elements and annealing at 800°C, the ternary rare-earth germanides RE 3Ru2Ge3 and RE 3Ir2Ge3 have been prepared for most of the smaller RE components (RE=Y, Gd–Tm, Lu). In the iridium-containing reactions, the new phases RE 2IrGe2 were also generally formed as by-products. Powder X-ray diffraction revealed orthorhombic Hf3Ni2Si3-type structures (space group Cmcm, Z=4) for RE 3 M 2Ge3 (M=Ru, Ir) and monoclinic Sc2CoSi2-type structures (space group C2/m, Z=4) for RE 2IrGe2. Full crystal structures were determined by single-crystal X-ray diffraction for all members of RE 3Ru2Ge3 (a=4.2477(6)Å, b=10.7672(16)Å, c=13.894(2)Å for RE=Y; a=4.2610(3)–4.2045(8)Å, b=10.9103(8)–10.561(2)Å, c=14.0263(10)–13.639(3)Å in the progression of RE from Gd to Lu) and for Tb3Ir2Ge3 (a=4.2937(3)Å, b=10.4868(7)Å, c=14.2373(10)Å). Both structures can be described in terms of CrB- and ThCr2Si2-type slabs built from Ge-centred trigonal prisms. However, band structure calculations on Y3Ru2Ge3 support an alternative description for RE 3 M 2Ge3 based on [M 2Ge3] layers built from linked MGe4 tetrahedra, which emphasizes the strong M–Ge covalent bonds present. The temperature dependence of the electrical resistivity of RE 3Ru2Ge3 generally indicates metallic behaviour but with low-temperature transitions visible for some members (RE=Gd, Tb, Dy) that are probably associated with magnetic ordering of the RE atoms. Anomalously, Y3Ru2Ge3 exhibits semiconductor-like behaviour of uncertain origin. Magnetic measurements on Dy3Ru2Ge3 reveal antiferromagnetic ordering at 3K and several unusual field-dependent transitions suggestive of complex spin reorientation processes. [ABSTRACT FROM AUTHOR]

Dirubidium pentacadmium tetraarsenide, Rb2Cd5As4, dirubidium pentazinc tetraantimonide, Rb2Zn5Sb4, and the solid-solution phase dirubidium pentacadmium tetra(arsenide/antimonide), Rb2Cd5(As,Sb)4 [or Rb2Cd5As3.00(1)Sb1.00(1)], have been prepared by direct reaction of the component elements at high temperature. These compounds are charge-balanced Zintl phases and adopt the orthorhombic K2Zn5As4-type structure (Pearson symbol oC44), featuring a three-dimensional [ M5 Pn4]2− framework [ M = Zn or Cd; Pn is a pnicogen or Group 15 (Group V) element] built of linked MPn4 tetrahedra, and large channels extending along the b axis which host Rb+ cations. The As and Sb atoms in Rb2Cd5(As,Sb)4 are randomly disordered over the two available pnicogen sites. Band-structure calculations predict that Rb2Cd5As4 is a small-band-gap semiconductor and Rb2Zn5Sb4 is a semimetal. [ABSTRACT FROM AUTHOR]

Ten quaternary arsenides AM1.5Tt0.5As2 (A = Na, K, Rb; M = Zn, Cd; Tt = Si, Ge, Sn) have been prepared by stoichiometric reactions of the elements at 600-650 °C. Seven of them (NaZn1.5Si0.5As2, NaZn1.5Ge0.5As2, NaZn1.5Sn0.5As2, NaCd1.5Sn0.5As2, KZn1.5Sn0.5As2, KCd1.5Sn0.5As2, RbCd1.5Sn0.5As2) adopt the trigonal CaAl2Si2-type structure (Pearson symbol hP5, space group P3m1, Z = 1, a = 4.0662(3)-4.4263(7) Å, c = 7.4120(5)-8.4586(14) Å), whereas the remaining three (KZn1.5Si0.5As2, KZn1.5Ge0.5As2, RbZn1.5Ge0.5As2) adopt the tetragonal ThCr2Si2-type structure (Pearson symbol tI10, space group I4/mmm, Z = 2, a = 4.0613(10)-4.1157(5) Å, c = 14.258(3)-14.662(2) Å). Both structure types contain anionic [M1.5Tt0.5As2] slabs that are built from edge-sharing tetrahedra and that stack alternately with nets of A cations. A structure map delineates the formation of these structure types for AM1.5Tt0.5As2 as a function of simple radius ratios. Although these arsenides have charge-balanced formulations, band structure calculations on NaZn1.5Tt0.5As2 (Tt = Si, Ge, Sn) indicate that semimetallic behavior is predicted as a result of overlap of the valence and conduction bands. [ABSTRACT FROM AUTHOR]

Abstract: The ternary rare-earth zinc arsenides REZn2As3 (RE=La–Pr) have been prepared by reactions of the elements at 800°C. They adopt new tetragonal structure types, with the La member (space group I4/mmm, Z=4, a=4.1133(2)Å, c=32.1246(14)Å) differing from the Ce and Pr members (space group P4/nmm, Z=2, a=4.0804(6)–4.0534(12)Å, c=16.089(5)–16.059(10)Å, respectively) in the disposition of RE-centred square antiprisms on opposite sides of square As nets. The structures contain thick anionic slabs, built from edge-sharing ZnAs4 tetrahedra, that can be considered either as stackings of three PbO-type layers or as fragments of the fluorite-type structure. These slabs are deficient in Zn and are reminiscent of the same features in binary arsenide Zn3As2. LaZn2As3 exhibits temperature-independent paramagnetism whereas CeZn2As3 follows modified Curie–Weiss behavior consistent with Ce3+ species but with no occurrence of long-range ordering. [Copyright &y& Elsevier]

Abstract: Experimental results of X-ray diffraction and X-ray photoelectron spectroscopy of fossil cutin from the compressed foliage of the Carboniferous tree fern Alethopteris pseudograndinioides, Cantabrian age, Sydney Coalfield, Canada, are presented in this paper. The light-colored cutin was obtained by oxidizing the compression in Schulze''s solution in two stages for a total of 19days. The broad peak in the powder diffractogram at 20° is characteristic of an average separation of ~4.4Å between the methylenic hydrocarbon chains (CH2)n, whereas the sharper peaks at 26°–28° suggest that within a small fraction of the sample, the chains are more regularly separated. Most of the chains are likely randomly aligned to form a nematic structure. Elemental composition by mass amounts to 58.3% C, 1.1% N, 19.4% O, 19.7% Cl, and 1.5% Si, and the local chemical environment of C 1s, O 1s, and Cl 2p is probed. Cl content is a surprising result, and further research is needed for identifying chlorine-containing species. [Copyright &y& Elsevier]

The pnictides RE2Mn3Cu9Pn7 (Pn = P, As) have been prepared by stoichiometric reaction of the elements at 800 °C. They are quaternary ordered variants of the hexagonal Zr2Fe12P7-type structure (Pearson symbol hP21, space group P6..., Z = 1; a = 9.6444(3)-9.5970(7) Å, c = 3.9027(1)-3.776l(3) Á for RE2Mn3Cu9P7 (RE = La-Nd, Sm, Gd-Dy); a = 9.9376(6)-9.9130(3) Â, c = 4.0194(2)-3.961l(1) Å for RE2Mn3Cu9Pn7 (RE = La--Nd)). Of the four possible sites available for the transition metal, the square pyramidal site (CN5) is occupied preferentially by Mn atoms, whereas the three tetrahedral sites (CN4) are occupied by Cu atoms. On proceeding to smaller RE members in the RE2Mn3Cu9Pn7 series, one of the transition-metal-centered polyhedra (Cu1) tends to become less distorted, while die remaining three (Cu2, Cu3, Mn4) become more distorted. Band structure calculations on La2Mn3Cu9P7 confirm that Mn--P and Cu--P contacts provide the strongest bonding interactions. Electrical resistivity measurements on Ce2Mn3Cu9P7 reveal metallic behavior with transitions at 165 and 18 K, probably of magnetic origin. [ABSTRACT FROM AUTHOR]

Abstract: The ternary arsenide BaAg2As2 has been prepared by reaction of the elements at 850°C. Single-crystal and powder X-ray diffraction analysis revealed that it adopts the ThCr2Si2-type structure (Pearson symbol tI10, space group I4/mmm, Z=2, a=4.6025(3)Å, c=10.8672(6)Å at 295K) featuring [Ag2As2] layers interconnected by homoatomic As–As bonds along the c-direction. Band structure calculations indicate no gap at the Fermi level, and support the occurrence of strong As–As and weak Ag–Ag bonding. The asymmetric lineshape and the absence of a BE shift in the Ag 3d5/2 core-line peak relative to the element suggest delocalization of the Ag valence electrons. A significant negative BE shift (1.0eV) in the As 3d5/2 core-line peak relative to the element confirms the presence of anionic As atoms. A reversible transition is observed at 175K in the electrical resistivity, and is probably related to a structural phase transition. [Copyright &y& Elsevier]

Stoichiometric reaction of the elements at high temperature yields the ternary arsenides K.2ZnsAs4 (650 °C) and Rb2ZnsAs4 (600 °C). They adopt a new structure type (Pearson symbol oC44, space group Cmcm, Z = 4; a = 11.5758(5) Å, b = 7.0476(3) Å, c = 11.6352(5) Å for K2Zn5As4; a = 11.6649(5) Å, b = 7.0953(3) Å, c = 11.7585(5) Å for Rb2ZnsAs4) with a complex three-dimensional framework of linked ZnAs4 tetrahedra generating large channels that are occupied by the alkali-metal cations. An alternative and useful way of describing the structure is through the use of stellae quadrangulae each consisting of four ZnAs4 tetrahedra capping an empty central tetrahedron. These compounds are Zintl phases; band structure calculations on K2Zn5As4, and Rb2Zn5As4 indicate semiconducting behavior with a direct band gap of 0.4 eV. [ABSTRACT FROM AUTHOR]

Abstract: Four ternary pnictides AAg4 Pn 2 (A=Sr, Eu; Pn=As, Sb) were prepared by reactions of the elements at 850°C and their crystal structures were determined from single-crystal X-ray diffraction studies. These silver-containing pnictides AAg4 Pn 2 adopt the trigonal CaCu4P2-type structure (Pearson symbol hR21, space group R3̄m, Z=3; a=4.5555(6)Å, c=24.041(3)Å for SrAg4As2; a=4.5352(2)Å, c=23.7221(11)Å for EuAg4As2; a=4.7404(4)Å, c=25.029(2)Å for SrAg4Sb2; a=4.7239(3)Å, c=24.689(2)Å for EuAg4Sb2), which can be derived from the trigonal CaAl2Si2-type structure of the isoelectronic zinc-containing pnictides AZn2 Pn 2 by insertion of additional Ag atoms into trigonal planar sites within [M 2 Pn 2]2− slabs built up of edge-sharing tetrahedra. Band structure calculations on SrAg4As2 and SrAg4Sb2 revealed that these charge-balanced Zintl phases actually exhibit no gap at the Fermi level and are predicted to be semimetals. [Copyright &y& Elsevier]

The ternary arsenides A2Zn2As3 and the quaternary derivatives A2Ag2ZnAs3 (A = Sr, Eu) have been prepared by stoichiometric reaction of the elements at 800 °C. Compounds A2Zn2As3 crystallize with the monoclinic Ba2Cd2Sb3-type structure (Pearson symbol mC28, space group C2/m, Z = 4; a = 16.212(5) Å, b = 4.275(1) Å, c = 11.955(3) Å, β = 126.271(3)° for Sr2Zn2As3; a = 16.032(4) Å, b = 4.255(1) Å, c = 11.871(3) Å, β = 126.525(3)° for Eu2Zn2As3) in which CaAl2Si2-type fragments, built up of edge-sharing Zn-centered tetrahedra, are interconnected by homoatomic As-As bonds to form anionic slabs [Zn2As3]4- separated by A2+ cations. Compounds A2Ag2ZnAs3 crystallize with the monoclinic Yb2Zn3Ge3-type structure (Pearson symbol mC32, space group C2/m; a = 16.759(2) Å, b = 4.4689(5) Å, c = 12.202(1) Å, β = 127.058(1)° for Sr2Ag2ZnAs3; a = 16.427(1) Å, b = 4.4721(3) Å, c = 11.9613(7) Å, β = 126.205(1)° for Eu2Ag2ZnAs3), which can be regarded as a stuffed derivative of the Ba2Cd2Sb3-type structure with additional transition-metal atoms in tetrahedral coordination inserted to link the anionic slabs together. The Ag and Zn atoms undergo disorder but with preferential occupancy over four sites centered in either tetrahedral or trigonal planar geometry. The site distribution of these metal atoms depends on a complex interplay of size and electronic factors. All compounds are Zintl phases. Band structure calculations predict that Sr2Zn2As3 is a narrow band gap semiconductor and Sr2Ag2ZnAs3 is a semimetal. Electrical resistivity measurements revealed band gaps of 0.04 eV for Sr2Zn2As3 and 0.02 eV for Eu2Zn2As3, the latter undergoing an apparent metal-to-semiconductor transition at 25 K. [ABSTRACT FROM AUTHOR]

Ternary rare-earth zinc arsenides REZn3As3 (RE = La—Nd, Sm) with polymorphic modifications different from the previously known defect CaAl2Si2-type forms, and the corresponding rare-earth cadmium arsenides RECd3As3 (RE = La—Pr), have been prepared by reaction of the elements at 800 °C. LaZn3As3 adopts a new orthorhombic structure type (Pearson symbol oP28, space group Pnma, Z = 4, a = 12.5935(8) Å, b = 4.1054(3) Å, c = 11.5968(7) Å) in which ZnAs4 tetrahedra share edges to form ribbons that are fragments of other layered arsenide structures; these ribbons are then interconnected in a three-dimensional framework with large channels aligned parallel to the b direction that are occupied by La3+ cations. All remaining compounds adopt the hexagonal ScAl3C3-type structure (Pearson symbol hP14, space group P63/mmc, Z = 2; a = 4.1772(7)-4.1501(2) Å, c = 20.477(3)-20.357(1) Å for REZn3As3 (RE = Ce, Pr, Nd, Sm); a = 4.4190(3)-4.3923(2) Å, c = 21.4407(13)-21.3004(8) Å for RECd3As3 (RE = La-Pr)) in which [M3As3]3- layers (M = Zn, Cd), formed by a triple stacking of nets of close-packed As atoms with M atoms occupying tetrahedral and trigonal planar sites, are separated by La3+ cations. Electrical resistivity measurements and band structure calculations revealed that orthorhombic LaZn3As3 is a narrow band gap semiconductor. [ABSTRACT FROM AUTHOR]

Abstract: The ternary rare-earth zinc arsenides REZn1−x As2 (RE=La–Nd, Sm) were prepared by reaction of the elements at 800°C. Single-crystal and powder X-ray diffraction analysis revealed a defect SrZnBi2-type average structure for the La member (Pearson symbol tI16, space group I4/mmm, Z=4; a=4.0770(9)Å, c=20.533(5)Å), in contrast to defect HfCuSi2-type average structures for the remaining RE members (Pearson symbol tP8, space group P4/nmm, Z=2; a=4.0298(5)–3.9520(4)Å, c=10.222(1)–10.099(1)Å in the progression from Ce to Sm). The homogeneity range is not appreciable (estimated to be narrower than 0.6<1−x<0.7 in SmZn1−x As2) and the formula REZn0.67As2 likely represents the Zn-rich phase boundary. The Ce–Nd members are Curie–Weiss paramagnets. LaZn0.67As2 shows activated behavior in its electrical resistivity, whereas SmZn0.67As2 exhibits anomalies in its temperature dependence of the electrical resistivity. [Copyright &y& Elsevier]

Abstract: The quaternary rare-earth phosphides RECuZnP2 (RE=Pr, Nd, Gd–Tm, Lu) have been prepared by reaction of the elements at 900°C, completing this versatile series which forms for nearly all RE metals. They adopt the trigonal CaAl2Si2-type structure (Pearson symbol hP5, space group P3̄m1, Z=1), as confirmed by single-crystal X-ray diffraction analysis on ErCuZnP2 and powder X-ray diffraction analysis on the remaining members. The Cu and Zn atoms are assumed to be disordered over the single transition-metal site. Band structure calculations on a hypothetically ordered YCuZnP2 model suggest a semimetal, with a zero band gap between the valence and conduction bands. This electronic structure is supported by XPS valence band spectra for RECuZnP2 (RE=Gd–Er), in which the intensity drops off smoothly at the Fermi edge. The absence of a band gap permits the electron count to deviate from the precise value of 16 e− per formula unit, as demonstrated by the formation of a solid solution in GdCu x Zn2−x P2 (1.0≤x≤1.3), while still retaining the CaAl2Si2-type structure. Because the Cu 2p XPS spectra indicate that the Cu atoms are always monovalent, the substitution of Cu for Zn leads to a decrease in electron count and a lowering of the Fermi level in the valence band. The magnetic susceptibility of RECuZnP2 (RE=Gd–Er), which obeys the Curie–Weiss law, confirms the presence of trivalent RE atoms. [ABSTRACT FROM AUTHOR]

The rare-earth iron arsenides RE12Fe57.5As41 (RE = La, Ce) have been prepared by direct reactions of the elements in the presence of a Sn flux. Analysis of single-crystal X-ray diffraction data reveals that they adopt a new orthorhombic structure type (Pearson symbol oP236, space group Pmmn, Z = 2; a = 10.8881(9) Å, b = 25.753(2) Å, c = 12.5436(10) Å for RE = La; a = 10.8376(8) Å, b = 25.639(2) Å, c = 12.4701(9) Å for RE = Ce). In this metal-rich arsenide, the complex three-dimensional network (derived from 4 RE, 24 Fe, and 17 As sites) can be described as being built from unusual wavelike layers of connected As-centered trigonal prisms. Five of the Fe sites are partially occupied. The electronic structure of these compounds was probed through core-line X-ray photoelectron spectra. Magnetic susceptibility measurements indicated ferromagnetic ordering at TC = 125 and 95 K for the La and Ce compounds, respectively. Electrical resistivity measurements on single crystals of Ce12Fe57.5As41 showed metallic behavior with a prominent transition that coincides closely with the ferromagnetic ordering temperature. [ABSTRACT FROM AUTHOR]

The title compounds are prepared from the elements (alumina crucible, 600-650 °C, 10 d). [ABSTRACT FROM AUTHOR]

Arc-melting and annealing of the elements (evacuated silica tubes, 800 °C, 1 week) is used to prepare ≈50 new quaternary germanides of the series Ln4M2InGe4 (Ln: Ce-Lu except Eu and Yb; M: Fe, Co, Ni, Ru, Rh, Ir) and a different but closely related series Ln4RhInGe4. [ABSTRACT FROM AUTHOR]

The title compounds are prepared from the elements (800 °C, 10 d) and characterized by powder and single crystal XRD, electrical resistivity measurements, and TB-LMTO-ASA band structure calculations. [ABSTRACT FROM AUTHOR]

Three series of quaternary pnictides, LnCuZnAs2 (Ln: Y, La-Nd, Sm, Gd-Lu), LnAgZnP2 (Ln: La-Nd, Sm, Gd-Dy), and LnAgZnAs2 (Ln: La-Nd, Sm, Gd-Dy) are prepared by solid reaction of the elements (evacuated silica tubes, 1. [ABSTRACT FROM AUTHOR]

The new title compounds (RE: Y, La-Er) are prepared from stoichiometric mixtures of the elements at 1050 °C (14 d) for the sulfides and at 900 °C (5 d) for the selenides, respectively. [ABSTRACT FROM AUTHOR]

The title compounds are prepared from stoichiometric mixtures of the elements (silica tubes, 1050 °C, 96 h) and characterized by powder and single crystal XRD, XPS, magnetic susceptibility measurements, and TB-LMTO-ASA band structure calculations. [ABSTRACT FROM AUTHOR]

The title compounds are synthesized from stoichiometric mixtures of the elements (alumina crucibles, 600 °C, 10 d) and characterized by single crystal XRD and TB-LMTO-ASA band structure calculations. [ABSTRACT FROM AUTHOR]

Ln4Mn2InGe4 (Ln: La Nd, Sm, Gd-Tm, Lu) are prepared by arc melting of stoichiometric mixtures the elements and annealing at 800 °C (evacuated silica tubes, 12 d). [ABSTRACT FROM AUTHOR]

Rb2Cd5As4 (I), Rb2Zn5Sb4 (II) and the solid solution Rb2Cd5(As,Sb)4 (III) are prepared by melting of the elements (Nb tubes in evacuated silica ampule; (I): 923 K, 7 d, ice quenching, (II): 823 K, 10 d, cooling rate 3 K/h). [ABSTRACT FROM AUTHOR]

The compounds Ln3M2Ge3 (Ln: Y, Gd-Tm, Lu; M: Ru, Ir) are prepared by arc melting of the elements and subsequent annealing at 800 °C for 12 d. [ABSTRACT FROM AUTHOR]

Ten quaternary arsenides of title are prepared by reaction of stoichiometric mixtures of the elements (alumina crucible, 600-650 °C, 10 d). [ABSTRACT FROM AUTHOR]

The title compounds are synthesized from the elements (silica tubes, 800 °C, 7 d) and characterized by powder XRD, single crystal XRD, magnetic measurements, and TB-LMTO band structure calculations. [ABSTRACT FROM AUTHOR]

The pnictides Ln2Mn3Cu9P7 (Ln: La-Nd, Sm, Gd-Dy) and Ln2Mn3Cu9As7 (Ln: La-Nd) are prepared from stoichiometric mixtures of the elements (800 °C, 14 d). [ABSTRACT FROM AUTHOR]

The title compound is synthesized by reaction of a stoichiometric mixture of the elements (alumina crucible, 850 °C for 2 d and 800 °C for 7 d). [ABSTRACT FROM AUTHOR]

The title compounds are prepared from stoichiometric mixtures of the elements (alumina crucible, 650 °C for K sample, 600 °C for Rb sample, 10 d) and characterized by single crystal XRD and TB-LMTO-ASA band structure calculations. [ABSTRACT FROM AUTHOR]

The new title compounds are prepared by reactions of stoichiometric mixtures of the elements (alumina crucible, 850 °C, 1-4 d) and characterized by single crystal XRD. [ABSTRACT FROM AUTHOR]

The quaternary rare-earth sulfides Nd 7 FeInS 13 and Pr 7 CoInS 13 were prepared by reactions of the elements at 1050 °C. Single-crystal X-ray diffraction revealed that they adopt a new orthorhombic structure type (space group Pnma , Z =4; a =11.2079(5) Å, b =3.9686(2) Å, and c =44.1642(18) Å for Nd 7 FeInS 13 ; a =11.2303(6) Å, b =3.9876(2) Å, and c =44.506(2) Å for Pr 7 CoInS 13 ). The structure contains two types of one-dimensional chains extending along the b -direction: corner-sharing tetrahedra centred by transition-metal atoms ( M = Fe, Co), and edge-sharing octahedra centred by In atoms. The RE atoms ( RE = Nd, Pr) are coordinated in monocapped or bicapped trigonal prismatic geometry. In terms of these RE -centred trigonal prisms, the structure of Nd 7 FeInS 13 and Pr 7 CoInS 13 can be considered to be built up of fragments of the structures of Y 2 HfS 5 and RE 2 S 3 (β-Cr 3 C 2 -type). Magnetic measurements on Pr 7 CoInS 13 indicated paramagnetic behaviour with no transitions down to 2 K. [ABSTRACT FROM AUTHOR]

The novel quaternary thiogermanate Li4CdGe2S7 (tetralithium cadmium digermanium heptasulfide) was discovered from a solid‐state reaction at 750 °C. Single‐crystal X‐ray diffraction data were collected and used to solve and refine the structure. Li4CdGe2S7 is a member of the small, but growing, class of I4–II–IV2–VI7 diamond‐like materials. The compound adopts the Cu5Si2S7 structure type, which is a derivative of lonsdaleite. Crystallizing in the polar space group Cc, Li4CdGe2S7 contains 14 crystallographically unique ions, all residing on general positions. Like all diamond‐like structures, the compound is built of corner‐sharing tetrahedral units that create a relatively dense three‐dimensional assembly. The title compound is the major phase of the reaction product, as evidenced by powder X‐ray diffraction and optical diffuse reflectance spectroscopy. While the compound exhibits a second‐harmonic generation (SHG) response comparable to that of the AgGaS2 (AGS) reference material in the IR region, its laser‐induced damage threshold (LIDT) is over an order of magnitude greater than AGS for λ = 1.064 µm and τ = 30 ps. Bond valence sums, global instability index, minimum bounding ellipsoid (MBE) analysis, and electronic structure calculations using density functional theory (DFT) were used to further evaluate the crystal structure and electronic structure of the compound and provide a comparison with the analogous I2–II–IV–VI4 diamond‐like compound Li2CdGeS4. Li4CdGe2S7 appears to be a better IR nonlinear optical (NLO) candidate than Li2CdGeS4 and one of the most promising contenders to date. The exceptional LIDT is likely due, at least in part, to the wider optical bandgap of ∼3.6 eV. [ABSTRACT FROM AUTHOR]

The new compounds Li2Mg2Si2S6 and Li2Mg2Ge2S6 have been prepared via traditional high‐temperature, solid‐state synthesis. The title compounds crystallize in the polar, noncentrosymmetric, trigonal space group P31m (No. 157) and adopt a new structure type featuring staggered, ethane‐like (T2S6)6− units, where T=Si or Ge. These (T2S6)6− units are nestled within the holes of magnesium‐sulfide "layers" that are created through the edge‐sharing of MgS6 octahedra. The holes found in the lithium‐sulfide "layers", created by LiS6 edge‐sharing octahedra, remain vacant, containing no (T2S6)6− anionic group. Through the face sharing of the respective MgS6 and LiS6 octahedra, the magnesium‐sulfide and lithium‐sulfide "layers" are stitched together resulting in an overall three‐dimensional structure. The optical bandgaps of Li2Mg2Si2S6 and Li2Mg2Ge2S6 are 3.24 and 3.18 eV, respectively, as estimated from optical diffuse reflectance UV‐Vis‐NIR spectroscopy. The compounds exhibit second harmonic generation responses of ∼0.24×KDP and ∼2.92×α‐quartz for Li2Mg2Si2S6 and ∼0.17×KDP and ∼2.08×α‐quartz for Li2Mg2Ge2S6, using a Nd:YAG laser at 1.064 μm. Electronic structure calculations were performed using density functional theory and the linearized augmented plane‐wave approach within the WIEN2k software package. Examination of the electronic band structures shows that these compounds are indirect bandgap semiconductors. [ABSTRACT FROM AUTHOR]

The new, quaternary diamond-like semiconductor (DLS) Cu4MnGe2S7 was prepared at high-temperature from a stoichiometric reaction of the elements under vacuum. Single crystal X-ray diffraction data were used to solve and refine the structure in the polar space group Cc. Cu4MnGe2S7 features [Ge2S7]6− units and adopts the Cu5Si2S7 structure type that can be considered a derivative of the hexagonal diamond structure. The DLS Cu2MnGeS4 with the wurtz-stannite structure was similarly prepared at a lower temperature. The achievement of relatively phase-pure samples, confirmed by X-ray powder diffraction data, was nontrival as differential thermal analysis shows an incongruent melting behaviour for both compounds at relatively high temperature. The dark red Cu2MnGeS4 and Cu4MnGe2S7 compounds exhibit direct optical bandgaps of 2.21 and 1.98 eV, respectively. The infrared (IR) spectra indicate potentially wide windows of optical transparency up to 25 μm for both materials. Using the Kurtz–Perry powder method, the second-order nonlinear optical susceptibility, χ(2), values for Cu2MnGeS4 and Cu4MnGe2S7 were estimated to be 16.9 ± 2.0 pm V−1 and 2.33 ± 0.86 pm V−1, respectively, by comparing with an optical-quality standard reference material, AgGaSe2 (AGSe). Cu2MnGeS4 was found to be phase matchable at λ = 3100 nm, whereas Cu4MnGe2S7 was determined to be non-phase matchable at λ = 1600 nm. The weak SHG response of Cu4MnGe2S7 precluded phase-matching studies at longer wavelengths. The laser-induced damage threshold (LIDT) for Cu2MnGeS4 was estimated to be ∼0.1 GW cm−2 at λ = 1064 nm (pulse width: τ = 30 ps), while the LIDT for Cu4MnGe2S7 could not be ascertained due to its weak response. The significant variance in NLO properties can be reasoned using the results from electronic structure calculations. [ABSTRACT FROM AUTHOR]

Abstract: The CaCu4P2-type pnictides EuAg4As2 and EuAg4Sb2 both contain stable divalent europium. Temperature dependent magnetic susceptibility measurements revealed experimental magnetic moments of 7.91(1) and 8.00(1) μB/Eu atom for the arsenide and antimonide, respectively. This is supported by 151Eu Mössbauer spectra which show isomer shifts of −11.33(1) (EuAg4As2) and −11.71(1) mm/s (EuAg4Sb2). Both pnictides show antiferromagnetic ordering below Néel temperatures of 14.9(5) (EuAg4As2) and 11.0(5) K (EuAg4Sb2). The antiferromagnetic ground state is only stable at low field strength. Metamagnetic transitions occur at critical field strengths of 4.4 (arsenide) and 2.4 kOe (antimonide) with saturation near 7 μB at 80 kOe and 5 K, indicating full parallel spin alignment. This is expressed by large magnetic hyperfine fields of 27.6(1) and 26.2(1) T at the europium nuclei of EuAg4As2 and EuAg4Sb2, respectively. 121Sb data of EuAg4Sb2 show a transferred hyperfine field of 9.8(2) T. [Copyright &y& Elsevier]

Abstract: The ternary rare-earth-metal chromium gallides RE 4CrGa12 (RE=Tb–Tm) have been prepared by reactions of the elements at 1000°C in the presence of excess gallium used as a self-flux. Their structures are derived by inserting Cr atoms into a quarter of the empty Ga6 octahedral clusters found in the parent binary gallides REGa3 (AuCu3-type), although single-crystal X-ray diffraction studies suggest that complex superstructures may be adopted. An ideal ordered Y4PdGa12-type structure was successfully refined for a crystal of Dy4CrGa12 (Pearson symbol cI34, space group Im m, Z=2, a=8.572(1)Å). Magnetic measurements on single-crystal samples reveal ferromagnetic or possibly ferrimagnetic ordering for the Tb, Dy, and Er members (T C=22, 15, and 2.8K, respectively) and antiferromagnetic ordering for the Ho member (T N=7.5K). Band structure calculations on a hypothetical “Y4CrGa12” model suggest that the Cr atoms carry no local magnetic moment. [Copyright &y& Elsevier]

The novel I 4 -II-IV 2 -VI 7 quaternary diamond-like semiconductors (DLSs), Cu 4 ZnGe 2 S 7 and Cu 4 CdGe 2 S 7 , were prepared from the constituent elemental powders at elevated temperatures. Cu 4 ZnGe 2 S 7 crystallizes in the polar, chiral space group C 2 and adopts the Cu 4 NiSi 2 S 7 structure-type, which can be considered a derivative of the cubic diamond structure. The cadmium analog takes on the Cu 5 Si 2 S 7 structure-type, which is related to the hexagonal diamond structure, and displays polar, Cc space group symmetry. Both compounds contain [Ge 2 S 7 ]6- anions created by corner-sharing GeS 4 tetrahedra. The crystal structures were carefully evaluated using: 1) extended connectivity tables, 2) minimum bounding ellipsoid analysis, and 3) bond valence sum (BVS) and global instability index (G) calculations. Both compounds are thermally stable up to temperatures exceeding 950 °C and melt incongruently. As assessed using diffuse reflectance spectroscopy, Cu 4 ZnGe 2 S 7 and Cu 4 CdGe 2 S 7 possess optical bandgaps of 1.65 eV and 1.90 eV, respectively, which are narrower than the analogous I 2 -II-IV-VI 4 DLSs. Electronic structure calculations show that both compounds are direct-bandgap semiconductors with significant contributions of Cu- d and S- p orbitals to the states at the top of the valence band. While Cu 4 CdGe 2 S 7 displays a weak second harmonic generation (SHG) response, the second-order nonlinear optical susceptibility, χ(2), of Cu 4 ZnGe 2 S 7 is 14.8 ± 1.5 pm V-1, assessed using the Kurtz-Perry powder method and an optical-grade AgGaSe 2 (AGSe) reference. Both compounds exhibit laser-induced damage threshold values similar to AGSe, ∼0.1 GW cm-2, for λ = 1.064 µm using picosecond laser pulses. Most importantly, Cu 4 ZnGe 2 S 7 exhibits a phase-matching behavior at λ = 3.1 µm. These results suggest that Cu 4 ZnGe 2 S 7 holds potential for use in low-powered laser applications involving efficient wave mixing in the mid-IR region. [Display omitted] • Cu 4 ZnGe 2 S 7 is a novel diamond-like material with the Cu 4 NiSi 2 S 7 structure type. • Cu 4 CdGe 2 S 7 is a novel diamond-like material with the Cu 5 Si 2 S 7 structure type. • Optical bandgaps of Cu 4 ZnGe 2 S 7 and Cu 4 CdGe 2 S 7 are 1.65 and 1.90 eV, respectively. • Cu 4 ZnGe 2 S 7 has χ (2) value of 14.8 ± 1.5 pm V− 1 and is phase matching for λ = 3.1 µm. • Cu 4 ZnGe 2 S 7 is a candidate for low-powered laser applications in the mid-IR region. [ABSTRACT FROM AUTHOR]

Eighteen isotypic, lithium-containing rare-earth sulfides, crystallizing in the chiral, polar, and noncentrosymmetric space group P 6 3 with the La 3 CuSiS 7 -structure type have been prepared via direct combination of the elements or binary sulfides; nine of these compounds are reported for the first time. The structures of these compounds, with the formulae Ln 3 LiTS 7 (Ln = La, Ce, Pr, Nd, Sm, Gd, and Dy for T = Si or Ge; Ln = La, Ce, Pr, and Nd for T = Sn), were determined by single crystal X-ray diffraction. According to X-ray powder diffraction data, the Ln 3 LiTS 7 compounds are the major phase of the reaction products. All of the compounds are semiconductors with optical bandgaps spanning nearly the entire visible region. The Si- and Ge-containing analogs show high thermal stability,> 1000 °C, while the Sn-containing compounds melt in the vicinity of ~740 °C. The compounds show potentially broad regions of optical transparency in the infrared regime. Calculated bond valence sums (BVSs) and global instability index (G) values confirm the Ln3+ oxidation state and stable crystal structures with reasonable strain, respectively. Ce 3 LiGeS 7 and Ce 3 LiSnS 7 display non-phase-matching but significant second-harmonic generation responses with χ 2 values of 21 ± 1 and 28 ± 1 pm/V, respectively at λ = 1.8 µm. The laser-induced damage threshold values for Ce 3 LiGeS 7 and Ce 3 LiSnS 7 are> 3 × commercial AgGaSe 2 , for picosecond pulses at λ = 1.064 µm. These two compounds also exhibit moderate third-harmonic generation responses. Additionally, crystal-chemical correlations are discussed. [Display omitted] • Nine new members of the La 3 CuSiS 7 family have been discovered, e.g. Ce 3 LiSiS 7. • Ce 3 LiGeS 7 and Ce 3 LiSnS 7 show second-harmonic generation with χ 2 values of> 20 pm/V. • The laser-induced damage thresholds for Ce 3 LiGeS 7 and Ce 3 LiSnS 7 are ~3 × AgGaSe 2. • Ce 3 LiGeS 7 and Ce 3 LiSnS 7 display moderate third-harmonic generation responses. [ABSTRACT FROM AUTHOR]