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1.
采用晶种法直接合成了硅铝比(SiO_2/Al_2O_3物质的量比)为137、224和309的三种Al-ITQ-13分子筛,并采用粉末X射线衍射(XRD)、扫描电镜(SEM)、N_2吸附-脱附、固体核磁共振(MAS NMR)和NH_3-程序升温脱附(NH_3-TPD)等分析方法对不同硅铝比分子筛进行了表征,并在固定床微型反应评价装置上,考察了硅铝比对甲醇转化制丙烯反应性能的影响。结果表明,不同硅铝比Al-ITQ-13分子筛呈现出相似的织构性质,酸量及酸强度随着硅铝比的升高逐渐下降。硅铝比对甲醇转化反应的产物分布存在较大的影响;随着硅铝比的升高,氢转移反应和芳构化反应活性降低,使得乙烯选择性下降,而丙烯和丁烯的选择性升高。硅铝比由137提高到309,丙烯的选择性(质量分数)由46.04%增加到55.52%,而丙烯/乙烯比由3.39提高到6.57。 相似文献
2.
The complexes M(CO) 2(PPh 3) 3 (I, M = Fe; II, M = Ru) readily react with H 2 at room temperature and atmospheric pressure to give cis-M(H) 2(CO) 2(PPh 3) 2 (III, M = Fe;IV,M = Ru). I reacts with O 2 to give an unstable compound in solution, in a type of reaction known to occur with II which leads to cis-Ru(O 2)(CO) 2(PPh 3) 2(V). Even compound IV reacts with O 2 to give V with displacement of H 2; this reaction has been shown to be reversible and this is the first case where the displacement of H 2 by O 2 and that of O 2 by H 2 at a metal center has been observed. III and IV are reduced to M(CO) 3(PPh 3) 2 by CO with displacement of H 2; Ru(CO) 3- (PPh 3) 2 is also formed by treatment of IV with CO 2, but under higher pressure. Compounds II and IV react with CH 2CHCN to give Ru(CH 2CHCN)(CO) 2- (PPh 3) 2(VI) which reacts with H 2 to reform the hydride IV. cis-Ru(H) 2(CO) 2(PPh 3) 2(IV) has been studied as catalyst in the hydrogenation and isomerization of a series of monoenes and dienes. The catalysts are poisoned by the presence of free triphenylphosphine. On the other hand the ready exchange of H 2 and O 2 on the “Ru(CO) 2(PPh 3) 2” moiety makes IV a catalyst not irreversibly poisoned by the presence of air. It has been found that even Ru(CO) 2(PPh 3) 3(II) acts as a catalyst for the isomerization of hex-1-ene at room temperature under an inert atmosphere. 相似文献
3.
The reaction of MoO 3 with various oxides of manganese (MnO, Mn 2O 3, Mn 3O 4 and MnO 2) and with MnCO 3 has been studied in air and nitrogen atmospheres employing DTA, TG and X-ray diffraction methods, with a view to elucidating the conditions for the formation of MnMoO 4. Thermal decomposition of MnCO 3 has also been studied in air and nitrogen atmospheres to help understand the mechanism of the reaction between MnCO 3 and MoO 3. The studies reveal that, whereas MnO, Mn 2O 3 and MnO 2 react smoothly with MoO 3 to form MnMoO 4, Mn 3O 4 does not react with MoO 3 in the temperature range investigated (48O–6OO°C). An equimolar mixture of MnCO 3 and MoO 3 reacts in air to yield MnMoO 4, while only a mixture of Mn 3O 4 and MoO 3 remains as final product when the same reaction is carried out in nitrogen. Marker studies reveal that manganese ions are the main diffusing species in the reaction between MoO 3 and manganese oxides that result in MnMoO 4. 相似文献
4.
The photochemical reaction of piperazine with C 70 produces a mono‐adduct (N(CH 2CH 2) 2NC 70) in high yield (67 %) along with three bis‐adducts. These piperazine adducts can combine with various Lewis acids to form crystalline supramolecular aggregates suitable for X‐ray diffraction. The structure of the mono‐adduct was determined from examination of the adduct I 2N(CH 2CH 2) 2NI 2C 70 that was formed by reaction of N(CH 2CH 2) 2NC 70 with I 2. Crystals of polymeric {Rh 2(O 2CCF 3) 4N(CH 2CH 2) 2NC 70} n? nC 6H 6 that formed from reaction of the mono‐adduct with Rh 2(O 2CCF 3) 4 contain a sinusoidal strand of alternating molecules of N(CH 2CH 2) 2NC 70 and Rh 2(O 2CCF 3) 4 connected through Rh?N bonds. Silver nitrate reacts with N(CH 2CH 2) 2NC 70 to form black crystals of {(Ag(NO 3)) 4(N(CH 2CH 2) 2NC 70) 4} n?7 nCH 2Cl 2 that contain parallel, nearly linear chains of alternating (N(CH 2CH 2) 2NC 70 molecules and silver ions. Four of these {Ag(NO 3)N(CH 2CH 2) 2NC 70} n chains adopt a structure that resembles a columnar micelle with the ionic silver nitrate portion in the center and the nearly non‐polar C 70 cages encircling that core. Of the three bis‐adducts, one was definitively identified through crystallization in the presence of I 2 as 12{N(CH 2CH 2) 2N} 2C 70 with addends on opposite poles of the C 70 cage and a structure with C2v symmetry. In 12{I 2N(CH 2CH 2) 2N} 2C 70, individual 12{I 2N(CH 2CH 2) 2N} 2C 70 units are further connected by secondary I2???N2 interactions to form chains that occur in layers within the crystal. Halogen bond formation between a Lewis base such as a tertiary amine and I 2 is suggested as a method to produce ordered crystals with complex supramolecular structures from substances that are otherwise difficult to crystallize. 相似文献
5.
A reinvestigation of the reaction of Ir(CO)Cl(PPh 3) 2, 1 with HSnPh 3 has revealed that the oxidative-addition product Ir(CO)Cl(PPh 3) 2(H)(SnPh 3), 2 has the H and SnPh 3 ligands in cis-related coordination sites. Compound 2 reacts with a second equivalent of HSnPh 3 by a Cl for H ligand exchange to yield the new compound H 2Ir(CO)(SnPh 3)(PPh 3) 2, 3. Compound 3 contains two cis- related hydride ligands. Under an atmosphere of CO, 1 reacts with HSnPh 3 to replace the Cl ligand with SnPh 3 and one of the PPh 3 ligands with a CO ligand and also adds a second equivalent of CO to yield the 5-coordinate complex Ir(CO) 3(SnPh 3)(PPh 3), 4. Compound 4 reacts with HSnPh 3 by loss of CO and oxidative addition of the Sn-H bond to yield the 6-coordinate complex HIr(CO) 2(SnPh 3) 2(PPh 3), 5 that contains two trans-positioned SnPh 3 ligands. 相似文献
6.
Reactive species generated in the gas and in water by cold air plasma of the transient spark discharge in various N2/O2 gas mixtures (including pure N2 and pure O2) have been examined. The discharge was operated without/with circulated water driven down the inclined grounded electrode. Without water, NO and NO2 are typically produced with maximum concentrations at 50% O2. N2O was also present for low O2 contents (up to 20%), while O3 was generated only in pure O2. With water, gaseous NO and NO2 concentrations were lower, N2O was completely suppressed and HNO2 increased; and O3 was lowered in O2 gas. All species production decreased with the gas flow rate increasing from 0.5 to 2.2 L/min. Liquid phase species (H2O2, NO2 ̄, NO3 ̄, ·OH) were detected in plasma treated water. H2O2 reached the highest concentrations in pure N2 and O2. On the other hand, nitrites NO2 ̄ and nitrates NO3 ̄ peaked between 20 and 80% O2 and were associated with pH reduction. The concentrations of all species increased with the plasma treatment time. Aqueous ·OH radicals were analyzed by terephthalic acid fluorescence and their concentration correlated with H2O2. The antibacterial efficacy of the transient spark on bacteria in water increased with water treatment time and was found the strongest in the air-like mixture thanks to the peroxynitrite formation. Yet, significant antibacterial effects were found even in pure N2 and in pure O2 most likely due to high ·OH radical concentrations. Controlling the N2/O2 ratio in the gas mixture, gas flow rate, and water treatment time enables tuning the antibacterial efficacy. 相似文献
7.
Polymeric membrane-based gas separation technology has significant advantages compared with traditional amine-based CO 2 separation method. In this work, SEBS block copolymer is used as a polymer matrix to incorporate triethylene oxide (TEO) functionality. The short ethylene oxide segment is chosen to avoid crystallization, which is confirmed by differential scanning calorimetry and wide-angle X-ray scattering characterizations. The gas permeability results reveal that CO 2/N 2 selectivity increased with increasing content of TEO functional group. The highest CO 2 permeability (281 Barrer) and CO 2/N 2 selectivity (31) were obtained for the membrane with the highest TEO incorporation (57 mol%). Increasing the TEO content in these copolymers results in an increase in CO 2 solubility and a decrease in C 2H 6 solubility. For example, as the grafted TEO content increased from 0 to 57 mol%, the CO 2 solubility and CO 2/C 2H 6 solubility selectivity increased from 0.72 to 1.3 cm 3(STP)/cm 3 atm and 0.47 to 1.3 at 35°C, respectively. The polar ether linkage in TEO-grafted SEBS copolymers exhibits favorable interaction with CO 2 and unfavorable interaction with nonpolar C 2H 6, thus enhancing CO 2/C 2H 6 solubility selectivity. 相似文献
8.
The reactivity of neodymium diiodide, NdI 2 ( 1 ), towards organosilicon, ‐germanium and ‐tin halides has been investigated. Compound 1 readily reacts with Me 3SiCl in DME to give trimethylsilane (6 %), hexamethyldisilane (4 %) and (Me 3Si) 2O (19 %). The reaction with Et 3SiBr in THF results in formation of Et 3SiSiEt 3 (17 %) and Et 3SiOBu n (34 %). Alkylation of Me 3SiCl with Pr nCl in the presence of 1 in THF affords Me 3SiPr n (10 %), Me 3SiOBu n (52 %) and Me 3SiSiMe 3 (1 %). The main product identified in the reaction mixture formed upon interaction of 1 with dichlorodimethylsilane Me 2SiCl 2 in THF is di‐ n‐butoxydimethylsilane Me 2Si(OBu n) 2 (54 %) together with minor amounts of Me 2Si(OBu n)Cl. The reaction of 1 with Me 3GeBr under the same conditions produces Me 3GeGeMe 3 (44 %), Me 3GeH (3 %), and Me 3GeI (7 %). An analogous set of products was obtained in the reaction with Et 3GeBr. Treatment of trimethyltin chloride with 1 causes reduction of the former to tin metal (74 %). Me 3SnH (7 %) and hexamethyldistannane (11 %) were identified in the volatile products. The reaction of 1 with Me 3SiI provides straightforward access to hepta‐coordinated NdI 3(THF) 4 ( 2 ), the structure of which was determined by X‐ray diffraction. 相似文献
9.
The bridging fluoroolefin ligands in the complexes [Ir 2(CH 3)(CO) 2(μ‐olefin)(dppm) 2][OTf] (olefin=tetrafluoroethylene, 1,1‐difluoroethylene; dppm=μ‐Ph 2PCH 2PPh 2; OTf ?=CF 3SO 3?) are susceptible to facile fluoride ion abstraction. Both fluoroolefin complexes react with trimethylsilyltriflate (Me 3SiOTf) to give the corresponding fluorovinyl products by abstraction of a single fluoride ion. Although the trifluorovinyl ligand is bound to one metal, the monofluorovinyl group is bridging, bound to one metal through carbon and to the other metal through a dative bond from fluorine. Addition of two equivalents of Me 3SiOTf to the tetrafluoroethylene‐bridged species gives the difluorovinylidene‐bridged product [Ir 2(CH 3)(OTf)(CO) 2(μ‐OTf)(μ‐C?CF 2)(dppm) 2][OTf]. The 1,1‐difluoroethylene species is exceedingly reactive, reacting with water to give 2‐fluoropropene and [Ir 2(CO) 2(μ‐OH)(dppm) 2][OTf] and with carbon monoxide to give [Ir 2(CO) 3(μ‐κ 1:η 2‐C?CCH 3)(dppm) 2][OTf] together with two equivalents of HF. The trifluorovinyl product [Ir 2(κ 1‐C 2F 3)(OTf)(CO) 2(μ‐H)(μ‐CH 2)(dppm) 2][OTf], obtained through single C? F bond activation of the tetrafluoroethylene‐bridged complex, reacts with H 2 to form trifluoroethylene, allowing the facile replacement of one fluorine in C 2F 4 with hydrogen. 相似文献
10.
The ability of B atoms on two different molecules to engage with one another in a noncovalent diboron bond is studied by ab initio calculations. Due to electron donation from its substituents, the trivalent B atom of BYZ 2 (Z=CO, N 2, and CNH; Y=H and F) has the ability to in turn donate charge to the B of a BX 3 molecule (X=H, F, and CH 3), thus forming a B⋅⋅⋅B diboron bond. These bonds are of two different strengths and character. BH(CO) 2 and BH(CNH) 2, and their fluorosubstituted analogues BF(CO) 2 and BF(CNH) 2, engage in a typical noncovalent bond with B(CH 3) 3 and BF 3, with interaction energies in the 3–8 kcal/mol range. Certain other combinations result in a much stronger diboron bond, in the 26–44 kcal/mol range, and with a high degree of covalent character. Bonds of this type occur when BH 3 is added to BH(CO) 2, BH(CNH) 2, BH(N 2) 2, and BF(CO) 2, or in the complexes of BH(N 2) 2 with B(CH 3) 3 and BF 3. The weaker noncovalent bonds are held together by roughly equal electrostatic and dispersion components, complemented by smaller polarization energy, while polarization is primarily responsible for the stronger ones. 相似文献
11.
The reaction of CdCl 2 or CdBr 2with LiBH 4, in ether yields no pure Cd(BH 4) 2, but Li 2Cd(BH 4) 4 was isolated as an oily etherate. Similarly, NaCd(BH 4) 3 was obtained from CdCl 2 and NaBH 4 in ether and tetrahydrofurane as solvents. LiCd(BH 4) 3 and NaCd(BH 4) 3 were also formed from the components in ether solution. In these solutions Cd migrates to the anode confirming their formulation as tetrahydroborato-cadmates. Cadmiumtetrahydroborate was formed in the reaction of cadmium methoxide with diborane in tetrahydrofurane (THF) and isolated as crystalline solvates. It reacts with pyridine to give Cd(BH 4) 2 · 3 NC 5H 5 and with NH 3 to yield Cd(NH 3) 6(BH 4) 2. 相似文献
12.
Samples in the system Lu 2−xY xSi 2O 7 (0? x?2) have been synthesized following the sol-gel method and calcined to 1300 °C, a temperature at which the β-polymorph is known to be the stable phase for the end-members Lu 2Si 2O 7 and Y 2Si 2O 7. The XRD patterns of all the compositions studied are compatible with the structure of the β-polymorph. Unit cell parameters are calculated as a function of composition from XRD patterns. They show a linear change with increasing Y content, which indicates a solid solubility of β-Y 2Si 2O 7 in β-Lu 2Si 2O 7 at 1300 °C. 29Si MAS NMR spectra of the different members of the system agree with the XRD results, showing a linear decrease of the 29Si chemical shift with increasing Y content. Finally, a correlation reported in the literature to predict 29Si chemical shifts in silicates is applied here to obtain the theoretical variation in 29Si chemical shift values in the system Lu 2Si 2O 7-Y 2Si 2O 7 and the results compare favorably with the values obtained experimentally. 相似文献
13.
The reactions of [Co 2(CO) 8] with E(SiMe 3) 2 (E = Se, Te) in CH 2Cl 2 result in the formation of the compounds [Co 4Se 2(CO) 10]> ( 1 ) and [Co 4Te 2(CO) 11] ( 2 ), respectively. Both cluster complexes have similar molecular structures in which the cobalt atoms form four‐membered rings with μ4‐bridging chalcogen atoms (Se and Te) above and below the plane of the metal atoms and the carbonyl ligands as either terminal or μ2‐bridging ligands. DFT‐calculations for both compounds have been carried out in order to obtain some more information about their electronic distribution. In the presence of the phosphine Ph 2PC≡CPPh 2 (dppa), the reaction of [Co 2(CO) 8] with Se(SiMe 3) 2 leads to the formation of [Co 8Se 4(CO) 16( μ‐dppa) 2] ( 3 ). During the reaction two molecules of [Co 2(CO) 8] have been added to the acetylene groups of the dppa ligands, whilst the remaining cobalt atoms coordinate to the phosphorus atoms of the phosphine. In this compounds the selenium atoms act as μ3‐ligands, bridging the metal atoms bonded to the phosphorus with those bonded to the acetylene groups. 相似文献
14.
The finding that compounds of the type (Me 3Si) 2(PhMe 2Si)CSiMePhX react with electrophiles to give very predominantly rearranged products (Me 3Si) 2(Ph 2MeSi)CSiMe 2Y, which would be expected to be thermodynamically disfavoured, can be rationalized in terms of a mechanism in which the anchimerically-assisted departure of X − gives the Ph-bridged cation [(Me 3Si) 2MePh] + which is attacked by the nucleophile at the less hindered centre bearing two Me groups rather than that bearing one Me and one Ph group, with the outcome determined by kinetic rather than thermodynamic factors. Both (Me 3Si) 2(Ph 2MeSi)CSiMe 2Br and its isomer (Me 3Si) 2(PhMe 2Si)CSiMePhBr react with AgBF 4 in CH 2Cl 2 or Et 2O to give >95% of the fluoride (Me 3Si) 2(Ph 2MeSi)CSiMe 2F. Reaction of the bromide (Me 3Si) 2(PhMe 2Si)CSiMePhBr with AgO 2CCF 3 in Et 2O, and that of the hydride (Me 3Si) 2(PhMe 2Si)CSiMePhH with ICl in CCl 4, likewise give >95% of the rearranged (Me 3Si) 2(Ph 2MeSi)CSiMe 2O 2CCF 3 and (Me 3Si) 2(Ph 2MeSi)CSiMe 2Cl, respectively. 相似文献
15.
Synthesis and Reactivity of the Diphenylphosphanyltrimethylsilylamine Ph 2PN(H)SiMe 3 The trimethylsilyliminotriphenylphosphoran Ph 3P=NSiMe 3 ( 1 ) reacts with sodium in THF under cleavage of one P–C phenyl bond leading to the P III‐species [(THF) 3Na(Ph 2PNSiMe 3)] ( 2 ). Reaction with NH 4Br or hydrolysis with water gives the diphenylphosphanyltrimethylsilylamine Ph 2PN(H)SiMe 3 ( 3 ) and in low yields the oxidized byproduct [(THF)Na(OOPPh 2)] n ( 4 ) that can be synthesised directly in high yields in the reaction of Ph 2POOH and NaH in THF. 3 was reacted with an equimolar amount of Zn{N(SiMe 3) 2} 2 to give [(Me 3Si) 2NZnPh 2PNSiMe 3] 2 ( 5 ). 3 reacts with caesium under phosphorus‐phosphorus bond formation in a reductive substituent coupling reaction to give [(THF)Cs 2{Ph(NSiMe 3)P} 2] n ( 6 ) where phosphorus(III) is reduced to phosphorus(II). Phosphorus‐phosphorus bond formation to give (Ph 2PNSiMe 3) 2 ( 7 ) where the phosphorus(III) centres are oxidized to P IV is observed in the reaction of 3 with n‐BuLi and bismuthtrichloride. 相似文献
16.
Reactions of Phosphorus(Arsenic)chalcogenides with Phosphorus(Arsenic)triiodide The specific heats and enthalpies of melting of the tetraphosphorustrithio(seleno)-diiodides have been determined. For the preparation of β-P 4S 3I 2 a new mthod by reacting P 4S 3 with PI 3 in CS 2 solution was found. Experiments to prepare compounds of the type As 4S 3I 2 by the classical methods for the preparation of the resp. phosphorus compounds failed. The reaction of As 4S 3 with AsI 3 leads to the formation of As 4S 4. The other sulphides of the As? S system As 2S 3 and As 4S 4 react with AsI 3 to AsSI, however, in the reaction of As 4S 4 the addition of S is necessary. 相似文献
17.
Here a unique single-crystal-to-single-crystal (SCSC) transformation of a 116-nuclear Au I72Cd II40Na I4 cage-of-cage ( 2 CdNa) is reported, which was created from a trigold(I) metalloligand with d -penicillamine by way of a 9-nuclear Au I6Cd II3 cage ( 1 ). Cage-of-cage 2 CdNa is composed of 12 cages of 1 that are linked by 4 Cd 2+ and 4 Na + ions, with its surface being covered by 12 NO 3− ions to form a discrete, spherical molecule with a diameter ca. 4.7 nm. In crystal 2 CdNa, the cage-of-cage molecules are packed in a cubic lattice with a huge cell volume of ca. 4.5×10 5 Å 3, so as to have large interstices with diameters of more than 3 nm. Upon soaking crystals 2 CdNa in aqueous Cu(NO 3) 2, all Cd 2+ and Na + were quickly exchanged by Cu 2+ to produce an analogous Au I72Cu II44 cage-of-cage ( 2 Cu) in a SCSC manner. Prolonged soaking led to the SCSC transformation to another supramolecular structure ( 2′ Cu) consisting of 152-nuclear Au I72Cu II80 cage-of-cages that are alternately H-bonded with the Au I72Cu II44 cage-of-cages. 2′ Cu showed the accommodation of MoO 42− and the conversion of MoO 42− to β-Mo 8O 264− in the crystal, with retention of single-crystallinity. 相似文献
18.
As 12Se 44—: a New Selenoarsenate Anion with a Polyarsenic Cage in the Compound [Co(NH 3) 6] 2As 12Se 4 · 12 NH 3 Orange coloured crystals of [Co(NH 3) 6] 2As 12Se 4 · 12 NH 3 were prepared by the reduction of As 4Se 4 with a solution of sodium in liquid ammonia and subsequent precipitation with CoBr 2. The X‐ray structure determination shows them to contain the selenoarsenate anion As 12Se 44—, which consists of a central As 12‐cage with four exo‐bonded, formally negatively charged Se atoms. The structure of the As 12‐cage is equivalent to the main polyphosphorus building unit of a known organopolyphosphane and of tubular P 12 in the compound (CuI) 3P 12. 相似文献
19.
The reactions of naphthalene in N 2O 5? NO 3? NO 2? N 2? O 2 reactant mixtures have been investigated over the temperature range 272–297 K at ca. 745 torr total pressure and at 272 K and ca. 65 torr total pressure using long pathlength Fourier transform infrared absorption spectroscopy. 2,3-Dimethyl-2-butene was added to the reactant mixtures at 272 K to rapidly scavenge the NO 3 radicals both initially present in the added N 2O 5 and formed from the thermal decomposition of N 2O 5 during the reactions. The data obtained in the presence and absence of added 2,3-dimethyl-2-butene showed that napthalene undergoes initial reaction with the NO 3 radical to form an NO 3-naphthalene adduct, which either rapidly decomposes back to the reactants (at a rate of ca. 5 × 10 5 s ?1 at 298 K) or reacts exclusively with NO 2 to form products. When NO 3 radicals, N 2O 5 and NO 2 are in equilibrium, this overall process is kinetically equivalent to reaction of naphthalene with N 2O 5, and previous kinetic and product studies have indeed assumed the reactions of naphthalene and alkyl-substituted naphthalenes in N 2O 5? NO 3? NO 2? air mixtures to be with N 2O 5, and not with NO 3 radicals. 相似文献
20.
Eu 5Ge 3 and EuIrGe 2 were prepared from the elements in tantalum tubes, and their crystal structures were determined from single crystal X-ray data. Eu 5Ge 3 adopts the structure of Cr 5B 3: I4/mcm, a = 799.0(1)pm, c = 1 536.7(1)pm, Z = 4, wR2 = 0.0421 for 669 F 2 values and 16 variables. The structure of Eu 5Ge 3 contains isolated germanium atoms and germanium atom pairs with a Ge? Ge distance of 256.0 pm. Eu 5Ge 3 may be described as a Zintl phase with the formulation [5 Eu 2+] 10+[Ge] 4?[Ge 2] 6?. Magnetic investigations of Eu 5Ge 3 show Curie-Weiss behaviour above 50 K with a magnetic moment of μ exp = 7.6(1) μ B which is close to the free ion value of μ eff = 7.94 μ B for Eu 2+. EuIrGe 2 is isotypic with CeNiSi 2: Cmcm, a = 445.5(2) pm, b = 1 737.4(4) pm, c = 426.6(1) pm, Z = 4, wR2 = 0.0507 for 295 F 2 values and 18 variables. The structure of EuIrGe 2 is an intergrowth of ThCr 2Si 2-like slabs with composition EuIr2Ge2 and AlB 2-like slabs with composition EuGe2 in an AB stacking sequence. Both slabs are distorted when compared to the symmetry of the prototypes. The Ge? Ge distance of 256.6 pm in the AlB 2-like fragment is comparable to that in Eu 5Ge 3. 相似文献
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