Single Crystal Research Articles

An Improved Ordinary State-Based Peridynamic Model for Granular Fractures in Cubic Crystals and the Effects of Crystal Orientations on Crack Propagation.

Material anisotropy caused by crystal orientation is an essential factor affecting the mechanical and fracture properties of crystal materials. This paper proposes an improved ordinary state-based peridynamic (OSB-PD) model to study the effect of arbitrary crystal orientation on the granular fracture in cubic crystals. Based on the periodicity of the equivalent elastic modulus of a cubic crystal, a periodic function regarding the crystal orientation is introduced into peridynamic material parameters, and a complete derivation process and expressions of correction factors are given. In addition, the derived parameters do not require additional coordinate transformation, simplifying the simulation process. Through convergence analysis, a regulating strategy to obtain the converged and accurate results of crack propagation paths is proposed. The effects of crystal orientations on crack initiation and propagation paths of single-crystal materials with different notch shapes (square, equilateral triangle, semi-circle) and sizes were studied. The results show that variations in crystal orientation can change the bifurcation, the number, and the propagation path direction of cracks. Under biaxial tensile loading, single crystals with semi-circular notches have the slowest crack initiation time and average propagation speed in most cases and are more resistant to fracture. Finally, the effects of grain anisotropy on dynamic fractures in polycrystalline materials under different grain boundary coefficients were studied. The decrease in grain anisotropy degree can reduce the microcracks in intergranular fracture and the crack propagation speed in transgranular fracture, respectively.

Heteronuclear Complexes of Hg(II) and Zn(II) with Sodium Monensinate as a Ligand.

The commercial veterinary antibiotic sodium monensinate (MonNa) binds mercury(II) or zinc(II) cations as thiocyanate [Hg(MonNa)2(SCN)2] (1) or isothiocyanate [Zn(MonNa)2(NCS)2] (2) neutral coordination compounds. The structure and physicochemical properties of 1 and 2 were evaluated by the methods of single crystal and/or powder X-ray diffraction, infrared, nuclear magnetic resonance, X-ray photoelectron spectroscopies, and electrospray-mass spectrometry. The primary cores of the two complexes comprise HgS2O2 (1) and ZnN2O2 (2) coordination motifs, respectively, due to the ambidentate binding modes of the SCN-ligands. The directly bound oxygen atoms originate from the carboxylate function of the parent antibiotic. Sodium cations remain in the hydrophilic cavity of monensin and cannot be replaced by the competing divalent metal ions. Zinc(II) binding does not influence the monensin efficacy in the case of Bacillus cereus and Staphylococcus aureus whereas the antimicrobial assay reveals the potential of complex 2 as a therapeutic candidate for the treatment of infections caused by Bacillus subtilis, Kocuria rhizophila, and Staphylococcus saprophyticus.

Fast growth of large-sized organic single crystals via spin coating

Spin-coating stands out as one of the fastest and simplest processes for material solidification. While it is commonly employed for producing polycrystalline thin films, recent endeavors have explored its potential for epitaxial growth, albeit primarily limited to inorganic materials. In this study, we demonstrate the spin-coating method enabling the rapid growth of large-sized organic single crystals (OSCs). Within 2 h, we successfully obtained OSCs with controlled lateral sizes of up to 2 mm, which conventionally takes several weeks using slow solvent evaporation. Raman mapping and UV–Vis absorption measurements confirmed the growths of the OSCs. We propose the growth mechanism by using the supersaturated dynamic fluid model. Furthermore, we demonstrate the device integration of these OSCs for charge-transfer complex channel, revealing ambipolar behavior during gate sweep. This innovative OSCs production method has the potential to advance the various field of science and electronics, traditionally hindered by the scarcity of adequately sized OSCs.

The dual action of N2 on morphology regulation and mass-transfer acceleration of CO2 hydrate film

The morphology characteristics of CH4, CO2 and CO2+N2 hydrate film forming on the suspending gas bubbles are studied using microscopic visual method at supercooling conditions from 1.0 to 3.0 K. The hydrate film vertical growth rate and thickness along the planar gas-water interface are measured to study the hydrate formation kinetics and mass transfer process. Adding N2 in the gas mixture plays the same role as lowering the supercooling conditions, both retarding the crystal nucleation and growth rates, which results in larger single crystal size and rough hydrate morphology. N2 in the gas mixture helps to delay the secondary nucleation on the hydrate film, which is beneficial to maintain the pore-throat structure and enhance the mass transfer. The vertical growth rate of hydrate film mainly depends on the supercooling conditions and gas compositions but has weak dependence with the experimental temperature and pressure. Under the same gas composition condition, the final film thickness shows a linear relationship with the supercooling conditions. The mass transfer coefficient of CH4 molecules in hydrates ranges from 4.54 to 7.54×10–8 mol·cm–2·s–1·MPa–1. The maximum mass transfer coefficient for CO2+N2 hydrate occurs at the composition of 60% CO2+40% N2, which is 3.98×10–8 mol·cm–2·s–1·MPa–1.

Full-operating-temperature tensile mechanisms of [111] oriented single-crystal superalloy: New intermediate temperature toughening behavior against ductility losing

Single crystal (SX) superalloys are required for full-operating-temperature mechanical properties. However, the quest for intermediate temperature (IT) resistance often encounters a perplexing phenomenon: anomalous yielding behavior coupled with an unexpected loss of ductility. This study delved into the tensile behavior of a [111]-oriented SX superalloy from room temperature (RT) to 1150 °C, uncovering temperature-dependent tensile mechanisms where the interplay among phases and deferent defects governs plastic deformation. Desirable high strength-ductility properties were observed at IT, showcasing comparable strength with increased ductility. Microstructural evidences show that the primary strengthening effects stem from coupled interface boundary strengthening and anti-phase boundary (APB) strengthening, while the plasticity arises from planer defects transitioning from the stacking fault (SF) within γ phase at small strains, to superlattice SFs, ultimately to the erasure of superlattice SFs, leaving cutting dislocation pairs in γʹ phase. Energy analysis of APB and SF, along with adherence to Schmid laws, reinforce the plausibility of such intricate defect interactions. The strength-ductility balance can be ascribed to the collective effect of preferentially generated dislocations and prompt formation of SF. This strategy of sequential defects’ competition provides a new route for solving the strength-ductility trade-off of alloys.

A comprehensive study of crystal structure, UV–visible study, electric-dielectric properties of a recently developed Hybrid Material [(C6H5N2)2ZnCl4]

The advanced hybrid material, [(C6H5N2)2ZnCl4] was prepared using the gradual dehydration process by combining 4-cyanopyridine and ZnCl2 under standard ambient temperature conditions. The compound underwent various characterization techniques, including single crystal and Powder X-ray diffractions (SXRD, PXRD), Scanning Electron Microscopy (SEM) and EDX Energy-Dispersive X-ray, FT-IR spectroscopy, UV–Visible absorption analysis, Hirshfeld surface analysis (SHG), and thermal analysis. The molecular composition of the examined chemical substances was determined to belong to the orthorhombic P212121 space group through single crystal X-ray analysis. analysis. Its molecular arrangement was characterized by alternating layers of tetrahedral [ZnCl4]2- and 4-cyanopyridinium planes (C6H5N2)+. These layers are connected through NH···Cl and CH···Cl hydrogen bonds, which contribute to their cohesion and overall adherence. The UV–visible spectrum using Tauc plot relation, has unveiled the energy ratio of an optical band gap, which is measured at 4.80 eV. Additionally, thermal analysis has demonstrated that [(C6H5N2)2ZnCl4] exhibits thermal stability up to a temperature of 475 K. SHG study was employed to examine the interactions between molecules. Additionally, 2D finger plots were utilized to quantitatively assess the impact of these interactions on the crystal structure. This work discusses various electrical characteristics obtained through impedance measurements, including dielectric constants and electric modulus. To shed light on the electrical resistance and dielectric characteristics, we conducted complex impedance spectroscopy at different frequencies with temperature ranging between 313 and 423 K. The elaborate Nyquist curve revealed a solitary semicircle, indicating that the signal was generated by a single capacitive circuit associated with the grain. We also researched ac conduction to figure out how electricity is transmitted. The diagram unveils that the conduction mechanism is thermally activated. The activation energy value obtained from the dc conductivity is approximately 0.768 eV. The analysed material allows for the movement of space charge through a hopping mechanism. Finally, the dielectric constant estimate demonstrates that this title compound is a suitable candidate for the fabrication of opto-electronic materials. Modulus analysis demonstrated that the mobile charge carriers exhibited mobility both at low and high frequencies, covering short and long distances.

Highly Luminescent TCNQ in Melamine.

Optical properties of molecules change drastically as a result of interactions with surrounding environments as observed in solutions, clusters, and aggregates. Here, we make 7,7,8,8-tetracyanoquinodimethane (TCNQ) highly luminescent by encapsulating it in crystalline melamine. Colored single crystals are synthesized by slow evaporation of aqueous tetrahydrofuran solutions of melamine and TCNQ. Single-crystal X-ray diffraction reveals the lattice structure of pure melamine, meaning that the color is of impurities. Both mass spectrometry and UV-vis spectroscopy combined with density-functional theory calculations elucidate that the impurity species are neutral TCNQ and its oxidation product, dicyano-p-toluoyl cyanide anion (DCTC-), whose concentrations in a melamine crystal can be controlled by adjusting the molar ratio between melamine and TCNQ in the precursor solution. Fluorescence excitation-emission wavelength mappings on the precursor solutions illustrate dominant emissions from DCTC- while the emission from TCNQ is quenched by the resonance energy transfer to DCTC-. On the contrary, TCNQ in crystalline melamine is a bright fluorophore whose emission wavelength centered at 450 nm with internal quantum yields as high as 19% and slow fluorescence lifetimes of about 2 ns. The method of encapsulating molecules into transparent melamine would make many other molecules fluorescent in solids.

Modeling of Cr3+ doped Cassiterite (SnO2) Single Crystals

Using the superposition model, the crystal field and zero-field splitting parameters of Cr3+ doped cassiterite (tin oxide), SnO2 single crystals are computed. For calculations, the appropriate locations for Cr3+ ions in SnO2 with distortion are taken into account. The experimental values and the zero-field splitting parameters in theory with local distortion agree fairly well. Using the Crystal Field Analysis Program and crystal field parameters, the optical energy bands for Cr3+ in SnO2 are calculated. The findings indicate that in SnO2 single crystals, one of the Sn4+ ions is replaced by Cr3+ ions.

Density functional theory calculations, structural and spectroscopic characterization, and solvent-dependent HOMO-LUMO studies of 2-nitro-4-methylanilinium benzenesulfonate

Single crystals of 2-nitro-4-methylanilinium benzenesulfonate were successfully grown from a water solution and the crystalline arrangement was determined through XRD analysis and confirms the centrosymmetric space group P21/c of the monoclinic system, with four molecules per unit cell. Furthermore, theoretical investigations were conducted at the B3LYP/6–311++G(d,p) level to explore the molecular structure, vibrational spectra, and bonding interactions of the grown compound and provides insights into the fundamental properties of the compound and its molecular behavior. In addition to theoretical studies, FMO & UV–Visible techniques were employed to investigate the electronic transitions and energy levels of the compound in both gas phase and various solvents (including water, methanol, acetone, benzene, heptane, and cyclohexane). This comprehensive analysis allows for an understanding of how the compound's electronic properties are influenced by solvent effects, providing valuable information for its potential applications. Furthermore, Hirshfeld surfaces (HS) and 2D fingerprint plots were utilized to analyze the interactions among the crystal's constituent elements and the factors influencing its structure. Finally, molecular docking evaluations were performed to assess the potential of the synthesized compound, 2-nitro-4-methylanilinium benzenesulfonate, as a drug candidate. This computational approach helps predict how the compound may interact with biological targets, providing valuable information for its potential therapeutic applications. Overall, this multidisciplinary approach offers a comprehensive understanding of the synthesized compound's structure, properties, and potential pharmaceutical relevance.

On the Thermal Dimorphy of the Strontium Perrhenate Sr[ReO4]2

AbstractHygroscopic single crystals of a new hexagonal high‐temperature modification of Sr[ReO4]2 were prepared from a melt of Sr[ReO4]2 ⋅ H2O and SrCl2 ⋅ 6 H2O. The structure analysis of the obtained crystals by X‐ray diffraction revealed that the title compound crystallizes in the ThCd[MoO4]3‐type structure with the hexagonal space group P63/m and the lattice parameters a=1023.81(7) pm and c=646.92(4) pm (c/a=0.632) for Z=2 in its quenchable high‐temperature form. Two crystallographically independent Sr2+ cations are coordinated by oxygen atoms forming either octahedra or tricapped trigonal prisms, whereas the Re7+ cations are found in the centers of discrete tetrahedral meta‐perrhenate units [ReO4]−. Temperature‐dependent in‐situ PXRD studies of dry powder samples of Sr[ReO4]2 exhibited its thermal dimorphy with a phase‐transition temperature at 500–550 °C from literature‐known m‐Sr[ReO4]2 into the newly discovered h‐Sr[ReO4]2 (hexagonal).

Synthesis, Stability, Meisenheimer Complex Formation, and Charge‐Transfer Properties of Ultra‐Electron‐Deficient Tetracyano‐Naphthalene Diimides

AbstractTetra‐cyano substituted naphthalene diimides (TCNDIs) with calculated LUMO of −5.2 eV, form one of the strongest electron‐acceptors known to date. However, the synthesis and isolation of this class of molecules remain challenging due to its reactivity emanating from its ultra‐electron‐deficiency. Herein we have established an improved synthetic methodology of TCNDIs with cost‐effective reagents and circumventing metallic catalysts. The synthesis is amenable to TCNDIs with the shortest axial alkyl groups, i. e., methyl group and also longer alkyl chains. We also gained insight on how axial alkyl chain lengths influence electron‐deficiency, Meisenheimer complex formation, reactivity, and charge‐transfer of TCNDIs from computation, spectroscopy, and electrochemical studies. The TCNDIs with Me/Et axial groups were found to be more susceptible to moist solvents vis‐à‐vis the TCNDIs with longer alkyl groups. The single crystal structures of the TCNDIs show infinitely π‐stacked structure, and a new C=O ⋅ ⋅ ⋅ C≡N or C≡N ⋅ ⋅ ⋅ π motif is discerned. Finally, toluene‐mediated charge‐transfer properties of TCNDIs in the single crystals as well as in solution have been examined.

Influence of Sputtering Power on the Properties of Magnetron Sputtered Tin Selenide Films.

The ecofriendly tin selenide (SnSe) is expected to find multiple applications in optoelectronic, photovoltaic, and thermoelectric systems. This work is focused on the thermoelectric properties of thin films. SnSe single crystals exhibit excellent thermoelectric properties, but it is not so in the case of polycrystalline bulk materials. The investigations were motivated by the fact that nanostructuring may lead to an improvement in thermoelectric efficiency, which is evaluated through a dimensionless figure of merit, ZT = S2 σ T/λ, where S is the Seebeck coefficient (V/K), σ is the electrical conductivity (S/m), λ is the thermal conductivity (W/mK), and T is the absolute temperature (K). The main objective of this work was to obtain SnSe films via magnetron sputtering of a single target. Instead of common radiofrequency (RF) magnetron sputtering with a high voltage alternating current (AC) power source, a modified direct current (DC) power supply was employed. This technique in the classical version is not suitable for sputtering targets with relatively low thermal and electrical conductivity, such as SnSe. The proposed solution enabled stable sputtering of this target without detrimental cracking and arcing and resulted in high-quality polycrystalline SnSe films with unprecedented high values of ZT equal to 0.5 at a relatively low temperature of 530 K. All parameters included in ZT were measured in one setup, i.e., Linseis Thin Film Analyzer (TFA). The SnSe films were deposited at sputtering powers of 120, 140, and 170 W. They had the same orthorhombic structure, as determined by X-ray diffraction (XRD), but the thickness and microstructure examined by scanning electron microscopy (SEM) were dependent on the sputtering power. It was demonstrated that thermoelectric efficiency improved with increasing sputtering power and stable values were attained after two heating-cooling cycles. This research additionally provides further insights into the DC sputtering process and opens up new possibilities for magnetron sputtering technology.

Molten flux growth of single crystals of quasi-1D hexagonal chalcogenide BaTiS3

BaTiS3, a quasi-1D complex chalcogenide, has gathered considerable scientific and technological interest due to its giant optical anisotropy and electronic phase transitions. However, the synthesis of high-quality BaTiS3 crystals, particularly those featuring crystal sizes of millimeters or larger, remains a challenge. Here, we investigate the growth of BaTiS3 crystals utilizing a molten salt flux of either potassium iodide, or a mixture of barium chloride and barium iodide. The crystals obtained through this method exhibit a substantial increase in volume compared to those synthesized via the chemical vapor transport method, while preserving their intrinsic optical and electronic properties. Our flux growth method provides a promising route toward the production of high-quality, large-scale single crystals of BaTiS3, which will greatly facilitate advanced characterizations of BaTiS3 and its practical applications that require large crystal dimensions. Additionally, our approach offers an alternative synthetic route for other emerging complex chalcogenides.Graphical

Ammonothermal Crystal Growth of Functional Nitrides for Semiconductor Devices: Status and Potential.

The state-of-the-art ammonothermal method for the growth of nitrides is reviewed here, with an emphasis on binary and ternary nitrides beyond GaN. A wide range of relevant aspects are covered, from fundamental autoclave technology, to reactivity and solubility of elements, to synthesized crystalline nitride materials and their properties. Initially, the potential of emerging and novel nitrides is discussed, motivating their synthesis in single crystal form. This is followed by a summary of our current understanding of the reactivity/solubility of species and the state-of-the-art single crystal synthesis for GaN, AlN, AlGaN, BN, InN, and, more generally, ternary and higher order nitrides. Investigation of the synthesized materials is presented, with a focus on point defects (impurities, native defects including hydrogenated vacancies) based on GaN and potential pathways for their mitigation or circumvention for achieving a wide range of controllable functional and structural material properties. Lastly, recent developments in autoclave technology are reviewed, based on GaN, with a focus on advances in development of in situ technologies, including in situ temperature measurements, optical absorption via UV/Vis spectroscopy, imaging of the solution and crystals via optical (visible, X-ray), along with use of X-ray computed tomography and diffraction. While time intensive to develop, these technologies are now capable of offering unprecedented insight into the autoclave and, hence, facilitating the rapid exploration of novel nitride synthesis using the ammonothermal method.

Anisotropic Optical Response of Ti-Doped VO2 Single Crystals.

This study delves into the effects of titanium (Ti) doping on the optical properties of vanadium dioxide (VO2), a material well known for its metal-to-insulator transition (MIT) near room temperature. By incorporating Ti into VO2's crystal lattice, we aim to uncover the resultant changes in its physical properties, crucial for enhancing its application in smart devices. Utilizing polarized infrared micro-spectroscopy, we examined TixV1-xO2 single crystals with varying Ti concentrations (x = 0.059, x = 0.082, and x = 0.187) across different crystal phases (the conductive rutile phase and insulating monoclinic phases M1 and M2) from the far-infrared to the visible spectral range. Our findings reveal that Ti doping significantly influences the phononic spectra, introducing absorption peaks not attributed to pure VO2 or TiO2. This is especially notable with polarization along the crystal growth axis, mainly in the x = 0.187 sample. Furthermore, we demonstrate that the electronic contribution to optical conductivity in the metallic phase exhibits strong anisotropy, higher along the c axis than the a-b plane. This anisotropy, coupled with the progressive broadening of the zone center infrared active phonon modes with increasing doping, highlights the complex interplay between structural and electronic dynamics in doped VO2. Our results underscore the potential of Ti doping in fine-tuning VO2's electronic and thermochromic properties, paving the way for its enhanced application in optoelectronic devices and technologies.

The peculiar molecular [(IF5)6(HF2)4]4− anion of the compound K4[(IF5)6(HF2)4

K4[(IF5)6(HF2)4] was obtained from the reaction of K[HF2] with liquid IF5. The compound was analyzed by single crystal and powder X‐ray diffraction, Raman spectroscopy, and quantum‐chemical calculations. It contains the largest molecular IF5/HF2− complex anion known so far. Surprisingly, the crystal structure of the A4B compound can be related to the Hg4Pt structure type.

The effect of annealing on micro-hardness of molybdenum single crystals

Molybdenum (Mo) crystals exhibit excellent mechanical properties such as high yield strength, high elastic modulus, very high melting point, and excellent corrosion resistance, making them a suitable choice for various industrial applications. The mechanical behaviour of these crystals has been investigated through tension, compression, and indentation experiments. The indentation experiments on annealed Mo single-crystal thin film show an increase in hardness with increase in annealing temperature from 400 °C–650 °C. However, it is not clear whether this behaviour is specific to the Mo thin films or these are applicable to the bulk samples of single crystals also. In order to address these issues, the Vickers indentation experiments are performed on as-received and annealed samples of (100) -, (110) -, and (111) -oriented Mo single crystals. The results show that the low-temperature annealing leads to an increase in micro-hardness by 9% for (100) oriented crystals. The x-ray diffraction (XRD), electron backscatter diffraction (EBSD) and energy dispersive x-ray spectroscopy (EDS) studies have shown that there is a drop in the number of dislocation sources or dislocation density ( ρ ) with no high-angle grain boundary formation or any microstructural changes or any oxide formation. This necessitates to enhance the applied stress required for significant yielding (or yield strength) which results in an increase in the hardness. Based on experimental observations, a hardening mechanism governed by dislocation annihilation during annealing has been proposed in the present study.

UoC-7: A Bimetallic K-Zn-MOF with an Anionic Framework Based on Fluorinated Trimesate Ligands Exhibiting a Large CO2 Uptake.

In solvothermal reactions of Zn(NO3)2×6H2O with K(H2mF-BTC) or K(H2dF-BTC) in DMF/ethanol or DMA/ethanol solvent mixtures, single crystals of the MOFs UoC-7(1F) and UoC-7(2F) were obtained crystallizing in the hexagonal space group P63/m (no.176) (H3BTC: 1,3,5-benzenetricarboxylic acid; mF-/dF: mono-/difluoro; DMF: N,N-dimethylformamide; DMA: N,N-dimethylacetamide; UoC: University of Cologne). According to the general composition [(CH3)2NH2][K2Zn3(mF-/dF-BTC)3(H2O)]×solvent, UoC-7 consists of an anionic bimetallic framework. The charge is compensated by a (CH3)2NH2 + cation stemming from the (partial) hydrolysis of the solvent. The crystal structure shows large channels along the hexagonal [001] direction, which accommodate the cations as well as solvent molecules. Surface areas (SBET) of 2740 m2/g (UoC-7(1F)) and 1643 m2/g (UoC-7(2F)) were obtained from N2 sorption measurements. UoC-7 shows structural similarities to the MOF NKU-521 with a 5-(1H-tetrazol-5-yl)isophthalate linker. Both MOFs exhibit a 4,7,8T14 topology. Despite smaller channels in UoC-7 compared to NKU-521, the CO2 uptake is considerably higher (~164 cm3/g at 1 bar/293 K) being one of the highest CO2 uptakes observed up to now.

Photo-triggered Phase Transition of Crystals and Photoactuation.

Photo-triggered phase transition is a new type of phase transition in which a photochromic crystal with a thermal phase transition transforms into an identical high-temperature phase in a temperature region lower than the thermal phase transition temperature upon light irradiation. Here, we report a second crystal that exhibits a photo-triggered phase transition, thereby demonstrating that the photo-triggered phase transition is a general phenomenon that occurs in crystals. When the chiral salicylidenephenylethylamine crystal was irradiated with ultraviolet (UV) light, the photo-triggered phase transition occurred in the temperature range -30 to -10 °C. The photo-triggered phase transition is induced by local stress due to trans-keto molecules produced by photoisomerization near the irradiated surface. Crystal cantilevers exhibited stepwise bending by the combination of the photo-triggered phase transition and photoisomerization. Alternate irradiation with UV and visible light achieved locomotion of single crystals driven by repeated stepwise bending. Finally, a detailed comparison of photo-triggered and non-photo-triggered phase transition crystals revealed that a sufficient molecular conformation change in affordable crystal voids, smooth photoisomerization, and most likely a chiral molecular arrangement are required for inducing the photo-triggered phase transition.

Nominal CaAl2Pt2 and Ca2Al3Pt – two new intermetallic compounds in the ternary system Ca–Al–Pt

Single crystals of CaAl2Pt2, Ca2Al3Pt and Ca2AlPt2 were initially observed in an attempt to synthesize Ca3Al4Pt4. Their structures were determined using single‐crystal X‐ray diffraction experiments. While nominal CaAl2Pt2 (CaBe2Ge2 type, P4/nmm, a = 426.79(2), c = 988.79(6) pm, wR2 = 0.0679, 246 F2 values and 18 variables) and Ca2Al3Pt (Mg2Cu3Si type, P63/mmc, a = 561.46(5), c = 876.94(8) pm, wR2 = 0.0664, 214 F2 values and 13 variables) exhibit Al/Pt mixing, for Ca2AlPt2 (Ca2Ir2Si type, C2/c, a = 981.03(2) b = 573.74(1), c = 772.95(2) pm, β = 101.862(1)° wR2 = 0.0307, 2246 F2 values and 25 variables) no mixing was observed. Subsequently, the nominal compositions were targeted with synthetic attempts from the elements using arc‐melting and annealing techniques. For CaAl2Pt2 and Ca2Al3Pt always multi‐phase mixtures were observed while Ca2AlPt2 could be obtained as almost X‐ray pure material. Quantum‐chemical calculations were used to investigate the charge transfer in these compounds rendering them polar intermetallics with a designated [AlxPty]δ– polyanion and Caδ+ cations in the cavities of the polyanions.