IUCrJ 13 (2026): 282–290 

https://doi.org/10.1107/S2052252526002782

Understanding structure at the atomic scale is fundamental for understanding the functioning and the development of materials with improved properties. Compared with other probes providing atomic resolution, electrons offer the strongest interaction in combination with minimal radiation damage, which makes them an ideal tool for investigating very small and radiation-sensitive samples [Henderson (1995), Q. Rev. Biophys. 28, 171–193]. However, these benefits are often offset by the laborious preparation of nanometre-sized samples that are not visible using a light microscope, and the fact that experiments are largely restricted to ultra-high vacuum [Duyvesteyn et al. (2018), Proc. Natl Acad. Sci. USA 115, 9569–9573; Gruene et al. (2021), Nat. Rev. Chem. 5, 660–668]. Here, we report the successful implementation of MeV electron diffraction for ab initio 3D structure determination of the quasi-2D material muscovite and the quantum material 1T-TaS2 at atomic resolution. By employing ultrashort electron pulses from the REGAE (Relativistic electron gun for atomic exploration) accelerator, we obtained high-quality diffraction datasets suitable for structural refinements based on dynamical scattering theory, enabling precise localization of even hydrogen atoms. The increased penetration depth of MeV electrons significantly expands the applicable thickness range of samples, overcoming previous restrictions associated with traditional electron diffraction. These findings establish MeVelectron diffraction as a viable approach for investigating a broad range of materials, including nanostructures and radiation-sensitive compounds, and open up new opportunities for in situ and time-resolved experiments [Chao et al. (2023), Chem. Rev. 123, 8347–8394; Filippetto et al. (2022), Rev. Mod. Phys. 94, 045004].

Acta Materialia 283 (2025): 120488

https://doi.org/10.1016/j.actamat.2024.120488

Additively manufactured components are generally heat treated to remove the undesired microstructure formed during the repeated heating-cooling cycles inherent to the process, known as intrinsic heat treatment (IHT). Recently, the IHT has been explored as a driving force for precipitation hardening in steels which can potentially shorten the manufacturing chain of AM components. However, the mechanisms behind the formation of secondary phase precipitates during the complex thermal history remains unclear. In this work, a combination of in situ high energy X-ray diffraction, atom probe tomography, scanning and transmission electron microscopy were used to reveal the precipitation sequence in an X40CrMoV5–1 tool steel during laser-directed energy deposition (L-DED). V-rich MCN and V₈CN₇ carbonitrides, as well as, Fe-Cr-rich M₃C and M₇C₃ carbides were formed at different stages of the L-DED. Their evolution and resulting chemical stoichiometry was correlated to the exact phase transformation occurring in the microstructure during the IHT over different regions along the built direction. Finally, the combined results from the in situ and ex situ experiments enabled us to retrace the history of the full microstructure during the L-DED process. The findings lead to the conclusion that secondary hardening effect in tool steel is, as expected, sensitive to the severity of the IHT, and if limited, can result in a tempered microstructure comparable to the ones conventionally obtained after tempering heat treatments.

IUCrJ 11 (2024): 977-990

https://doi.org/10.1107/S2052252524009722

Regolith draws intensive research attention because of its importance as the basis for fabricating materials for future human space exploration. Martian regolith is predicted to consist of defect-rich crystal structures due to long-term space weathering. The present report focuses on the structural differences between defect-rich and defect-poor forsterite (Mg₂SiO₄) – one of the major phases in Martian regolith. In this work, forsterites were synthesized using reverse strike co-precipitation and high-energy ball milling (BM). Subsequent post-processing was also carried out using BM to enhance the defects. The crystal structures of the samples were characterized by X-ray powder diffraction and total scattering using Cu and synchrotron radiation followed by Rietveld refinement and pair distribution function (PDF) analysis, respectively. The structural models were deduced by density functional theory assisted PDF refinements, describing both long-range and short-range order caused by defects. The Raman spectral features of the synthetic forsterites complement the ab initio simulation for an in-depth understanding of the associated structural defects.

Zeitschrift für Kristallographie - Crystalline Materials (2024)

https://doi.org/10.1515/zkri-2024-0078

To fabricate metals from the base materials for future Mars exploration, synthesis of representative olivine phases and their structural and spectroscopic characterizations are of crucial importance. Using mechanochemical technique that mimics the mechanical weathering, a complete solid solution of (Mg_1−xFe _x )₂SiO₄ has been synthesized to investigate the associated crystal chemical properties. X-ray powder diffraction data Rietveld analysis confirms that each polycrystalline sample crystallizes in space group Pbnm. The average crystallite size ranges between 80(1) nm and 223(4) nm. Each lattice parameter increases with increasing Fe-content due to the larger Fe²⁺ radius than that of Mg²⁺, following Vegard’s rule. For a given nominal chemical composition, substitution of Mg with Fe at the M1-site (4a: 0,0,0) is preferred to the M2-site (4c: x,y,¼). As a consequence, the average Fe-content lies slightly below the equivalence line for x = 0.2–0.8, indicating that the Fe/Mg ratio in the amorphous scattering content is most likely greater than unity. Characteristic Raman spectral features of the olivines have been explained in terms of the chemical composition (x). Simple regression models are demonstrated based on both X-ray diffraction and Raman spectroscopic data for the calculation of Mg/Fe in olivines. Diffuse reflectance UV/Vis spectra RATD analysis shows each olivine phase possesses direct band-gap between 3.38(3) eV and 4.90(3) eV. This study could keep valuable information to relevant databases for future human missions on Mars, in particular, for precise estimation of the representative olivines from the remote X-ray diffraction and spectroscopic data.

ChemCatChem (2024): e202400280

https://doi.org/10.1002/cctc.202400280

Nanoporous gold (npAu) attracted increasing attention over the last 20 years as a highly active and selective oxidation catalyst in particular at low temperatures. Previous research mainly focused on npAu that was fabricated by corrosive dealloying of AuAg parent alloys. Yet, the use of other binary alloys, such as AuCu, promises interesting variations of the catalytic properties, when considering that residual amounts of the less noble metal were shown to be co-catalytically involved. Aiming at providing a platform for systematic studies in this direction for Cu, we not only dealt with strategies for a reliable and reproducible preparation of npAu(Cu) catalysts from AuCu, but also with their potential for CO oxidation in comparison to npAu(Ag). We were able to develop an approach based on thermally quenched Au_0.3Cu_0.7 alloys, providing distinct synthetic advantages as a starting material for the catalyst fabrication versus the thermodynamically more stable AuCu₃ intermetallic compound. Using PCD (potentiostatically controlled dealloying), well-defined pore structures with ligament diameters of ∼40 nm and variable residual Cu concentrations in the range between ∼0.6 at % and ∼1.2 at % could be straightforwardly obtained. After activating such catalysts at 150 °C, they reproducibly showed catalytic activity for aerobic CO oxidation in a broad temperature window between 40 °C and 250 °C. As opposed to npAu(Ag), the activity increased with decreasing residual Cu content, outperforming the former at temperatures above ∼60 °C not only with respect to CO₂ formation rates but also with respect to thermal stability. Based on X-ray photoelectron spectroscopic and transmission electron microscopic results, it was possible to conclude that Cu segregates to the surface and, with rising Cu bulk content, increasingly occurs in form of Cu²⁺ species at the surface. While the latter are expected to be catalytically inactive, Cu and Cu⁺ species are likely candidates for the activation of oxygen being not possible on pure Au.

Science 385(6706) (2024): 318-321

DOI: 10.1126/science.adp4963

Nitrenes are a highly reactive, yet fundamental, compound class. They possess a monovalent nitrogen atom and usually a short life span, typically in the nanosecond range. Here, we report on the synthesis of a stable nitrene by photolysis of the arylazide M^SFluindN₃ (1), which gave rise to the quantitative formation of the arylnitrene M^SFluindN (2) (M^SFluind is dispiro[fluorene-9,3′-(1′,1′,7′,7′-tetramethyl-s-hydrindacen-4′-yl)-5′,9′′-fluorene]) that remains unchanged for at least 3 days when stored under argon atmosphere at room temperature. The extraordinary life span permitted the full characterization of 2 by single-crystal x-ray crystallography, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry, which supported a triplet ground state. Theoretical simulations suggest that in addition to the kinetic stabilization conferred by the bulky M^SFluind aryl substituent, electron delocalization across the central aromatic ring contributes to the electron stabilization of 2.

Journal of Crystallography - Crystalline Materials 239 (2024): 3-4

https://doi.org/10.1515/zkri-2023-0056

The presence of  ns ²  stereo-chemical active lone electron pairs (LEPs) causes asymmetric atomic environments around a given  p -block cation, leading to change the crystal chemistry of a respective system. Here we report a series of mullite-type compounds to understand at what extend Sr ²⁺  replaces the stereochemical active Pb ²⁺  cation in (Pb _{1− x} Sr _x )MnBO ₄ . Each member of the solid solution has been synthesized by conventional solid-state method. The polycrystalline samples are characterized using X-ray powder diffraction followed by Rietveld refinement. Substitution of Pb ²⁺  with Sr ²⁺  leads to contraction of the  a  lattice parameter with slight elongation in the  b  and  c  direction. For a difference of 1 pm of the ionic radius between Sr ²⁺  and Pb ²⁺ , the cell volume contracts about 4% between the end members as the spatial requirement of the LEP activity in the MBO ₄ ²⁻  channels significantly decreases. Within the solid solution, two distinct Pb/Sr–O ₂  bond distances significantly differ, which gradually decreases with increasing strontium content leading to a more symmetric coordination around strontium. The calculated BVS of Pb ²⁺ /Sr ²⁺  exhibits a linear correlation with the Wang–Liebau eccentricity parameter, indicating to an increased bonding ability cation. The vibrational properties are characterized by both Raman and FTIR spectroscopy, complementing the XPRD results. Electronic band gaps of selected (Pb _{1− x} Sr _x )MnBO ₄  samples were obtained from diffuse reflectance spectroscopy data. Additionally, the Sr containing samples show higher thermal stability than the Pb containing counterparts.    

Nature Communications 14 (2023): 6512

doi:  10.1038/s41467-023-41934-y

Structure-property relationships in ordered materials have long been a core principle in materials design. However, the introduction of disorder into materials provides structural flexibility and thus access to material properties that are not attainable in conventional, ordered materials. To understand disorder-property relationships, the disorder – ie, the local ordering principles – must be quantified. Local order can be probed experimentally by diffuse scattering. The analysis is notoriously difficult, especially if only powder samples are available. Here, we combine the advantages of three-dimensional electron diffraction – a method that allows single crystal diffraction measurements on sub-micron sized crystals – and three-dimensional difference pair distribution function analysis (3D-ΔPDF) to address this problem. In this work, we compare the 3D-ΔPDF from electron diffraction data with those obtained from neutron and x-ray experiments of yttria-stabilized zirconia (Zr _0.82 Y _0.18 O _1.91 ) and demonstrate the reliability of the proposed approach.

 © 2023 The Author(s) ( CC BY 4.0 )

Zeitschrift für Kristallographie - Crystalline Materials 238 (2023): 27 - 38

https://doi.org/10.1515/zkri-2022-0037

Sodalites of the general type |Na₈X₂|[T¹T²O₄]₆ with X = Cl⁻, Br⁻, I⁻ have been synthesized for Al–Si, Ga–Si, Al–Ge and Ga–Ge as T¹–T² frameworks. The structures were examined using in-house and synchrotron X-ray diffraction, Raman spectroscopy, force-field structure optimizations and DFT based ab-initio molecular dynamics (MD) computations. Calculated phonon density of states (PDOS) of the 12 compounds show only minor differences within a framework composition with a lowering of certain phonon energies with increasing anion size. Earlier published Debye and Einstein temperatures obtained with a Debye-Einstein-anharmonicity (DEA) model approach are confirmed using the determined low-temperature lattice parameters (18 K–293 K) and show no correlation with the respective PDOS. Small-box refinements against radial pair distribution functions (PDF) allowed the determination of anisotropic displacement ellipsoids (ADP) for Na⁺ and O²⁻, indicating a strong dependency of the ADP of Na⁺ on the chemical composition. Significantly lower thermal displacements from MD calculations suggested an influence of structural displacements. For compounds with an aspherical ADP for sodium, structural models could be refined in which the sodium is located on two 8e or one 24i site (both partially occupied), and also temperature-dependent (100 K–300 K) for the compounds with Ga–Ge framework. 3D-plots of the bond-valence sums of Na⁺ further validate the structural differences. These results imply that the local structure of halide-sodalites in many cases is not best described by the known average structure and may even not be cubic.

Z. Anorg. Allg. Chem. 648 (2022): e20220031

https://doi.org/10.1002/zaac.202200311

Polycrystalline red tin(II)oxide (RSO) has been synthesized by a fast reflux method. X-ray powder diffraction (XRPD) data Rietveld refinement confirms the orthorhombic space group Cmc2₁ (Z=8). The presence of 5 s² lone electron pair (LEP) of the Sn²⁺ cation results in layers of highly distorted SnO₄ tetrahedra with an averaged Wang-Liebau eccentricity (WLE) parameter of 4.3(1) x10⁻⁵ as a measure of the stereochemical activity. The significantly different Sn−O bond distances demonstrate the under-bonding nature of both the tin and the oxygen atoms in the SnO₄ coordination. The band gap of red tin(II)oxide is found to be 1.75(1) eV which is compared with those of blue-black tin(II) (BSO) and white tin(IV) oxide (WSO) based on the UV-Vis diffuse reflectance spectral data. Temperature-dependent XRPD reveals the phase transitions, which is complemented by thermogravimetric and differential scanning calorimetry (TG/DSC) investigations. Moreover, in-situ Raman spectroscopy additionally hints to an intermediate phase either of Sn₂O₃ or Sn₃O₄ appears within a short temperature range before the RSO to BSO transition occurs. Due to axial negative thermal expansion for the b-lattice parameter RSO exhibits nearly a zero thermal expansion coefficient for a given temperature range above room temperature.

Dalton Transactions 45 (2022): 4086

https://doi.org/10.1039/D2DT02447K

The double-perovskite series, Sr₂(Fe_1−xNi_x)TeO₆ (x = 0, 0.25, 0.50, 0.75, and 1) has been synthesized in polycrystalline form by solid-state reaction at 1300 K in air. Their crystal structures were probed by powder X-ray diffraction at room temperature. Rietveld analysis revealed that all samples crystallize in the monoclinic space group I2/m. The double-perovskite structures ideally contain two alternating types of octahedra (Fe/Ni)^2dO₆ and (Te)^2aO₆, tilted in the system (a⁻a⁻c⁰). However, the refinements have shown a complex distribution of all three cations over the two available octahedral sites; 2d (½, ½, 0) and 2a (0, 0, 0). Raman spectroscopy further complements the obtained results, by revealing a tiny increase of the wavenumber of some Raman modes when Fe is substituted by Ni. The optical characteristics of the series were determined by fitting diffuse reflectance UV/Vis spectra enabling the optical band gaps to be derived from Tauc method and derivation of absorption spectra fitting (DASF) techniques. Analyses of the obtained ⁵⁷Fe Mössbauer hyperfine parameters at room temperature of samples with compositions x = 0, 0.25, 0.50 and 0.75 reveal the presence of Fe³⁺ in high-spin state with an anti-site disorder of Fe–Ni–Te cations in distorted octahedral environments (site 2d and 2a). The results show that significant correlations exist between the crystal structures and physical properties of double perovskites containing B site transition elements of different charge and size. Temperature-dependent magnetic susceptibility data show magnetic transitions below 40(1) K (38(1) K, 31(1) K, 25(1) K, 20(1) K, and 35(1) K for x = 0, 0.25, 0.50, 0.75, and 1, respectively. A divergence between FC and ZFC curves for all compositions has been observed. The results show that the ground states of the doped materials might be spin glasses or magnetically ordered.

Journal of Materials Science 57 (2022): 19280-19299

https://doi.org/10.1007/s10853-022-07854-w

A new precursor for the formation of mullite-type visible-light active photocatalyst Bi₂Al₄O₉ has been identified. The crystal structure of the organic–inorganic hybrid perovskite can be described using the hexagonal setting of the rhombohedral unit cell with lattice parameters a = 1.1342(2) nm, c = 2.746(1) nm, and V = 3.059(2) nm³. The presence of di-nitro-glycerin as organic component, which is centered together with two bismuth atoms at the A-sites of the ABX₃-type perovskite, suggests for doubling of the a- and c-lattice parameters compared to isostructural BiAlO₃ perovskite. The nano-crystalline precursor with the chemical composition [Bi₂(C₃H₅N₂O₇)]Al₄[O₉(□_1-x(H₂O)_x)₃] (□: vacancies) decomposes at 540(10) K to a quantum-crystalline phase with an average crystallite size of 1.4(1) nm, refined from X-ray powder data Bragg reflections and confirmed by atomic pair distribution function data analysis. Further heating enables a controlled formation of quantum- or nano-crystalline mullite-type phases, depending on temperature and time. The same precursor structure could also be obtained as iron-containing phase and for Al/Fe solid-solution samples. UV/Vis diffuse reflectance spectroscopy suggests an indirect band-gap transition energy of 3.50(3) eV calculated by the Reflectance-Absorption-Tauc-DASF (RATD) method. Temperature-dependent UV/Vis allows to follow the change of band-gap energy across all associated phase transformations. The long- and short-range appearance of each phase has been presented using X-ray Bragg scattering and total scattering data analyses. This is supported by Raman and infrared spectroscopic investigations complemented by density functional theory (DFT) calculations. Moreover, the theoretical calculation confirms the incorporated di-nitro-glycerin. Thermal stabilities of the phases are investigated by using thermal analysis and temperature-dependent X-ray diffraction.

Crystal Growth and Design 22 (2022): 2557–2568

https://doi.org/10.1021/acs.cgd.2c00030

We demonstrate the growth of large (Mg,Zr):SrGa₁₂O₁₉ (SGMZ) single crystals and use a combination of X-ray imaging techniques to analyze their structural and chemical homogeneity. Single-crystal cylinders with lengths and diameters up to about 2.5 cm are achieved. Our characterization of polished sections reveals a localized (0001) facet that is typically formed at the center of the growth interface. Such facets are seen as the key factor limiting the growth of large-area crystals with excellent structural quality due to local deviations in the segregation behavior of the dopants. We developed a lab-based X-ray diffraction imaging technique with high sensitivity that exposes subtle variations in lattice parameters and lattice tilts, which are attributed to changes in the chemical composition and the resulting elastic deformation. The relationship between unit-cell dimensions and composition is verified by micro X-ray fluorescence mapping. In this way, we find a Ga-rich center region with a reduced unit-cell volume that is surrounded by a ring of increased tilt and elastic strain. Furthermore, we observe a 6-fold in-plane anisotropy of dopant incorporation and tree-ring-shaped structures caused by macrosteps. With rocking curve widths below 23 arcsec in ∼90% of the crystal, SGMZ crystals are largely homogeneous and hence suitable for the preparation of high-quality substrates. For most applications, the substantially enhanced crystal size enabled by very high Mg and Zr codoping levels outweighs the issues related to concentration variations arising from their addition.

Zeitschrift für Kristallographie - Crystalline Materials 237 (2022): 1-3

https://doi.org/10.1515/zkri-2022-0004

Twelve cubic sodalites |Na₈X₂|[T¹T²O₄]₆ (T¹ = Al³⁺, Ga³⁺; T² = Si⁴⁺, Ge⁴⁺; X = Cl⁻, Br⁻, I⁻) were examined using high-temperature (HT) X-ray diffraction experiments and TGA-DSC measurements. Temperature-dependent structure data was obtained by Rietveld refinements. Decomposition temperatures were determined using TGA-DSC data for all compounds. The temperature-dependent volume expansion was used to determine Debye and Einstein temperatures using DEA fits. Distinct relations between thermal expansion, bond lengths and the decomposition temperature could not be found. Determination of Lindemann constants of all compounds enables a classification of the sodalites in three groups.

Zeitschrift für Naturforschung B 75 (2020): 9-10

https://doi.org/10.1515/znb-2020-0159

Synthesis, crystal structure and temperature-dependent behavior of Na₂H₄Ga₂GeO₈ are reported. This novel gallogermanate crystallizes in space group I4₁/acd with room-temperature powder diffraction lattice parameters of a = 1298.05(1) pm and c = 870.66(1) pm. The structure consists of MO₄ (M = Ga, Ge) tetrahedra in four-ring chains, which are connected by two different (left- and right-handed) helical chains of NaO₆ octahedra. Protons coordinating the oxygen atoms of the GaO₄ tetrahedra not linked to germanium atoms ensure the charge balance. Structure solution and refinement are based on single crystal X-ray diffraction measurements. Proton positions are estimated using a combined approach of DFT calculations and NMR, FTIR and Raman spectroscopic techniques. The thermal expansion was examined in the range between T = 20(2) K and the compound’s decomposition temperature at 568(5) K, in which no phase transition could be observed, and Debye temperatures of 266(11) and 1566(65) K were determined for the volume expansion.

Zeitschrift für Kristallographie - Crystalline Materials 235 (2020): 6-7

https://doi.org/10.1515/zkri-2020-0027

The temperature-dependent structure-property relationships of the aluminosilicate perrhenate sodalite |Na₈(ReO₄)₂|[AlSiO₄]₆ (ReO₄-SOD) were analysed via powder X-ray diffraction (PXRD), Raman spectroscopy and heat capacity measurements. ReO₄-SOD shows two phase transitions in the investigated temperature range (13 K < T < 1480 K). The first one at 218.6(1) K is correlated to the transition of dynamically ordered P¯43n (> 218.6(1 K) to a statically disordered (<218.6(1) K) SOD template in P¯43n. The loss of the dynamics of the template anion during cooling causes an increase of disorder, indicated by an unusual intensity decrease of the 011-reflection and an increase of the Re-O₂ bond length with decreasing temperature. Additionally, Raman spectroscopy shows a distortion of the ReO₄ anion. Upon heating the thermal expansion of the sodalite cage originated in the tilt-mechanism causes the second phase transition at 442(1) K resulting in a symmetry-increase from P¯43n to Pm¯3n, the structure with the sodalites full framework expansion. Noteworthy is the high decomposition temperature of 1320(10) K.

Zeitschrift für Kristallographie - Crystalline Materials (2018) 234, Heft 4

https://doi.org/10.1515/zkri-2018-2122

The aluminosilicate iodide sodalite |Na₈I₂|[AlSiO₄]₆ was examined by temperature-dependent neutron time-of-flight powder diffraction from 5 K to 290 K and X-ray diffraction from 298 K to 1200 K. The temperature-dependent properties of the mean structure in space group P4̅3n were obtained by Rietveld analysis. A negative slope for the thermal expansion coefficient below 50 K could be observed, and the displacement parameters of the iodide ions indicate anharmonic effects. Local structure models (8×8×8 super cells) were refined against pair-distribution functions calculated from total scattering data collected at 5 K, 165 K and 240 K. The results indicate isotropic displacements for all atoms except for I-atoms, showing the effects of an anharmonic potential around this anion at very low temperatures.

The Journal of Physical Chemistry C (2018) 122 (49), 28280–28291

https://doi.org/10.1021/acs.jpcc.8b05740

We report on temperature-dependent structural and spectroscopic features of (Bi_1–xFe_x)FeO₃ perovskite for x = 0.15 and 0.25. Samples were synthesized by heating quantum crystalline precursors obtained by the polyol method. Crystal structures of each composition were obtained from in-house X-ray, synchrotron X-ray, and time-of-flight neutron powder diffraction data Rietveld refinements. Partial replacement of the Bi site by the Fe³⁺ cation significantly changes the crystal physicochemical properties, such as thermal expansion, polyhedral distortion, Debye temperature, and vibrational and magnetic properties. Whereas BiFeO₃ is multiferroic, both Bi_0.85Fe_0.15FeO₃ and Bi_0.75Fe_0.25FeO₃ are found to be superparamagnetic, as observed by temperature-dependent Mössbauer and SQUID measurements. Lattice thermal expansion was modeled using the Debye–Einstein-anharmonicity approach. Debye temperatures obtained from the mean-squared atomic displacement parameter and lattice thermal expansion are compared. Temperature dependence of selective Raman modes is also analyzed.

Journal of Solid State Chemistry (2017) 254, 82-89 

https://doi.org/10.1016/j.jssc.2017.07.013

The structural and spectroscopic features of the visible light photocatalyst Bi₂WO₆ have been studied. Polycrystalline (PC), nanocrystalline (NC) and quantum dot (QD) sized samples were produced using solid state reaction, hydrothermal and flame spray pyrolysis methods, respectively. While the crystal structures of PC and NC Bi₂WO₆ are well characterized using X-ray powder diffraction data Rietveld refinements, the structural information of the QD are obtained from the complementary pair distribution function analysis and high-resolution transmission electron microscopy. The Raman spectra of the samples are compared with the phonon density of states calculated by DFT. A continuous phenomenological model describes selective optical phonon confinement into the QDs. The type of the electronic bandgaps obtained from the UV-VIS absorbance-spectra have been analyzed using two different methods, and compared with those calculated from the electronic band structures.