Reduction In Lattice Parameter Research Articles

Bactericidal and in vitro osteogenic activity of nano sized cobalt-doped silicate hydroxyapatite

Hydroxyapatite (HA) particles with enhanced antibacterial properties can be prepared by integrating metal ions into the crystal structure of the nanoparticles. Cobalt and silicate ions containing HA (Co/Si-HA) with the formula Ca10-xCox(PO4)6-y(SiO4)y(OH)2 (x = 0.2, 0.6, and 1.0 and y = 0.5) was successfully synthesised by using microwave-assisted wet precipitation method. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and inductively coupled plasma mass spectrometry (ICP-MS) techniques were used to characterise the synthesised nanoparticles. The results revealed that the incorporation of SiO44− ions increased the lattice parameters and decreased the crystallite size of HA. However, the incorporation of Co2+ions led to the reduction of lattice parameters and the particle size of the SiHA nanoparticles. In vitro antibacterial activity of materials was evaluated using disk diffusion and minimum inhibitory concentration (MIC) protocols. The findings indicated that incorporating Co2+ ions into SiHA inhibited the growth of Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The cytotoxicity of materials evaluated using the Sarcoma osteogenic (Saos-2) cell line revealed that they were cytocompatible and exhibited no adverse side effects. The osteogenic differentiation of cells was confirmed by the significant increase in the alkaline phosphatase (ALP) activity by incorporating Co2+/SiO44− ions into the HA crystal structure. Our results show that the nanoparticles prepared in this study have a promising future in biomaterial-tissue engineering applications.

Effect of Cs partial substitution on crystal systems and bandgap values of MASnCl3

The development of Pb-free solar cells is crucial research to reduce the adverse impact of Pb on the environment and people. In this study, we have synthesized MA 1- x Cs x SnCl 3 (MA = CH 3 NH 3 ; x = 0–0.4) via solid-state reaction method. The reduction in lattice parameters and structural phase transition from triclinic to monoclinic at room temperature due to Cs partial substitution was investigated by powder X-ray diffraction (XRD). The reduction in lattice parameters is due to the size difference between MA and Cs. The decrease in the structural phase transition temperature to the cubic phase was revealed by differential scanning calorimetry (DSC). Ultraviolet–visible absorption spectroscopy revealed that bandgap values decrease as the amount of Cs partial substitution increases.

Enhanced performance of Pt-based diesel oxidation catalyst via defective MnOx: The role of Pt/MnOx interface

To strengthen the interface effect of Pt with MnOx, manganese oxides with different defective concentration were obtained via removing oxygen under reduction treatment. The excellent performance on the Pt-based oxidation catalyst with optimum reduction temperature is 250 °C, and it's the light-off temperature of CO, C3H6 and NO are 170 °C, 180 °C and 185 °C, respectively, and the highest NO maximum conversion of 76%. The defect on MnOx could induce the adsorption of Pt2+ to produce the higher platinum dispersion and more active oxygen species. The abundant oxygen vacancies on manganese manganite would transfer to the subsurface, reducing the Mn valence and affecting the electronic effect of Pt with MnOx. Meanwhile, the existence of interfacial structure induces the shrinkage of platinum cell with the reduction of lattice parameter, because of the doping of Mn ion. The strong interaction of Pt with MnOx could promote the reduction of manganese oxides at the lower temperature. The interface of Pt-MnOx could accelerate the oxygen mobility and facilitate the formation of more bridged nitrates and chelating nitrates. Due to the interfacial structure of Pt with MnOx, the low temperature catalytic performance and high NO conversion of catalyst are remarkably improved.

Theoretical investigation on the structure of mixed-metal zeolitic imidazolate framework and its interaction with CO2

Determining the effect of mixed-metal in metal–organic frameworks (MOFs) provides insight into how the distribution of various metal types affects their chemical bonding, electronic properties, particularly net atomic charge distribution and their interaction with guest molecules. In this report, the structural characteristic of the mixed-metal zeolitic imidazolate framework ZIF-8(Cd/Zn) has been thoroughly investigated, employing a periodic density functional theory approach to identify the effect of various locations of different metals. Increasing the fraction of Zn2+ in the mixed-metal ZIFs induces the reduction of lattice parameters and affects the bond distance between metal and linker. Moreover, identification of the chemical bonding present in the mixed-metal ZIFs provides an insight regarding the bond character of the metal to organic linker where Zn–N has a higher bond character than Cd–N, implying a different bond strength. Further confirmation was done by calculating the relative energy of the defective mixed-metal ZIF-8(Cd/Zn) by comparing when either Cd2+ or Zn2+ ions were removed from the structure. Furthermore, the interaction between CO2 and mixed-metal ZIF-8(Cd/Zn) in various positions yielded an overview where different CO2 location affects the binding energy. This study showed how the structure of mixed-metal ZIF-8(Cd/Zn) affects their electronic properties and its consequences on CO2 adsorption.

Advancing thermoelectrics by vacancy engineering and band manipulation in Sb-doped SnTe–CdTe alloys

A decrease in valence band energy offset can considerably improve the thermoelectric performance of SnTe, and alloying CdTe in SnTe has been confirmed to be efficient for inducing band convergence. However, the low solubility of CdTe in SnTe severely limits the further decrease in the energy offset and the reduction of lattice thermal conductivity. Inspired by the high solubility of Sb in SnTe-based thermoelectric materials, the trivalent Sb is introduced into SnTe–CdTe alloys, aiming at manipulating the thermoelectric transport properties. Combined with the valence band model, it is demonstrated that high concentration of Sb in SnTe–CdTe enables a further optimization in valence band structures, resulting in an improvement in density-of-state effective mass, thus significantly reinforces the power factor in the whole temperature range. Meanwhile, we propose the solid solution mode of Sb in SnTe, which always generates vacancies to balance the valence state, and the introduction of vacancies explains the reduced lattice parameters and almost constant carrier concentration. Particularly, the Debye–Callaway model quantitatively compares the contribution of Sb substitutional defects and vacancy defects. As a result, an enhanced zT of ∼1.1 has been achieved for Sn0.83Cd0.05Sb0.12Te at 823 K. This work clearly shows the critical role of Sb for enhancing the thermoelectric performance of SnTe–CdTe materials.

Evaluating the effects of structural disorder on the magnetic properties of Nd2Zr2O7

Motivated by the variation in reported lattice parameters of floating-zone-grown ${\mathrm{Nd}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ crystals, we have performed a detailed study of the relationship between synthesis environment, structural disorder, and magnetic properties. Using a combination of polycrystalline standards, electron-probe microanalysis, and scattering techniques, we show that crystals grown under atmospheric conditions have a reduced lattice parameter relative to pristine polycrystalline powders due to occupation of the Nd site by excess Zr (i.e., negative stuffing). In contrast, crystals grown under high-pressure Ar are nearly stoichiometric with an average lattice parameter approaching the polycrystalline value. While minimal disorder of the oxygen sublattices is observed on the scale of the average structure, neutron pair-distribution function analysis indicates a highly local disorder of the oxygen coordination, which is only weakly dependent on growth environment. Most importantly, our magnetization, heat capacity, and single-crystal neutron scattering data show that the magnetic properties of crystals grown under high-pressure Ar match closely with those of stoichiometric powders. Neutron scattering measurements reveal that the signature of magnetic moment fragmentation---the coexistence of all-in-all-out (AIAO) magnetic Bragg peaks and diffuse pinch-point scattering due to spin-ice correlations--persists in these nearly stoichiometric crystals. However, in addition to an increased AIAO transition temperature, the diffuse signal is seemingly stabilized and remains nearly unchanged upon warming to 800 mK. This behavior indicates that both the AIAO magnetic order and spin-ice correlations are sensitive to deviations of the Nd stoichiometry.

Effect of Nd doping on the structural, optical and dielectric properties of BaTi0.95Sn0.05O3 ceramics

Single-phase (Nd2x∕3Ba1−x)(Ti0.95Sn0.05)O3; NBTS, (x = 0.000, 0.005, 0.010 and 0.015) with tetragonal perovskite structures are synthesized by the conventional solid-state reaction method. The effect of Nd doping in BaTi0.95Sn0.05O3 has been studied for microstructural, optical, and dielectric properties. Rietveld refinement of XRD data confirms the phase purity of the sample. Doping of Nd leads to the reduction of lattice parameter and cell volume compared to the undoped sample. The dielectric constant and tangent loss for x = 0.005 i.e., 0.33% of Nd doped BaTi0.95Sn0.05O3 is ~3047 and 0.031 as compared to undoped sample (785 and 0.169), respectively. Minor quantities of Nd-doping in BaTi0.95Sn0.05O3 enhance the dielectric response by reducing dielectric loss. XPS study confirms the charge compensation in NBTS ceramics, which causes intrinsic defects and, strongly affects the dielectric properties of NBTS ceramics. The Nd doping also results in the transition from normal ferroelectrics to a relaxor-like ferroelectrics.

First-principles investigation of the elastic properties and phase stability of (Ti1-xNix)C1-y ternary metastable carbides

Recently, (Ti1-xNix)C1-y ternary metastable carbides have attracted considerable attention owing to their unique material properties; however, few studies have been conducted to reveal their elastic and phase stability properties. The present investigation revealed the elastic properties and phase stability of (Ti1-xNix)C1-y metastable carbides, depending on the nickel (Ni) and carbon (C) vacancy concentrations (x and y), using first-principles calculations. The results indicated that increasing the Ni and C vacancies generally reduced lattice parameters and elastic characteristics, particularly in the directional properties of carbides, such as shear and Young’s modulus. Debye temperature and Pugh’s criteria indicated that the rigidity and brittleness of carbides were effectively reduced by increasing the Ni and C vacancy concentrations. The degradation of the elastic properties caused by increasing the Ni content was explained by the low affinity of Ni and C, as well as the electron filling in the high-energy antibonding states of Ti–C bonds. First-principles thermodynamic analyses demonstrated that the generation of the C vacancy inevitably led to the formation of (Ti1-xNix)C1-y ternary metastable carbides based on thermodynamic stability. The results will elucidate the investigations on Ti-based ternary metastable carbide phases.

Role of 5 mol% Mg-Ni on the Structural and Magnetic Properties of Cobalt Chromates Crystallites Prepared by Solution Combustion Technique

The Co1 − (x + y)MgxNiyCr2O4(where, x = y = 0.00, 0.05) nanoparticles were synthesized by the solution combustion technique using a mixture of carbamide and glucose as fuel. The refined XRD study confirmed that samples are single-phased with spinel cubic structure having space group Fd3m. The difference in ionic radius of Co2+ ions and Mg2+, Ni2+ ions resulted in the reduction in lattice parameters. The stretching vibration modes are found at tetrahedral and octahedral site by using FTIR spectra. Force constant value also estimated from FTIR spectra. The magnetic transition was studied by using temperature-dependent magnetization. The magnetic transitions such as ferrimagnetism transition were observed at Curie temperature (TC = 98 K, 91 K for x = y = 0.00, 0.05, respectively), and spiral spin transition was observed at spiral temperature (TS = 26 K, 17 K for x = y = 0.00, 0.05, respectively). Both samples show higher magnetization below spiral transition temperature (TS).

Ferrimagnetic to antiferromagnetic transition and complex impedance analysis of Cr-doped magnesium ferrite nanoparticles

The chromium-doped magnesium ferrite (MgCrxFe2−xO4, x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0) were prepared using sol–gel technique. X-ray diffraction scans confirmed the cubic spinel structure for all the nanoparticles samples. Reduction in lattice parameter and average crystallite size with increasing Cr3+ concentration was observed due to smaller ionic radii of Cr3+ (0.67 A) ions as compared to Fe3+ (0.63 A) ions. In FTIR vibrational studies, the addition of Cr3+ shows the splitting of ν1 band into two sub-bands due to variation of bond strength between same cations present at tetrahedral and octahedral lattice sites. With increasing Cr3+ concentration, the ZFC–FC magnetic curves revealed a ferrimagnetic (FiM) to antiferromagnetic (AFM) transition as compound transformed from MgFe2O4 to MgCr2O4. The M–H loops revealed decrease in saturation magnetization with increase in Cr3+ concentration which is attributed to FiM to AFM transition. The coercivity showed a non-monotonic behavior and has maximum value of 750 Oe for x = 1.2 due to overlapping of blocking and Neel transition temperatures. The dielectric properties showed a decreasing trend with increasing Cr3+ concentration. The room temperature impedance spectroscopy (Nyquist plots) was simulated using equivalent RC circuit model and an appearance of second semi-circle in the Nyquist plot with increasing Cr3+ concentration is observed which can be attributed to the contribution of grains in the hooping mechanism.

Correlation between multifunctional properties of lead free Iron doped BCT perovskite ceramics

Present study investigates the effect of Fe doping on structural, microstructural, dielectric, ferroelectric, piezoelectric and magnetic properties of Barium calcium titanate (BCT) ceramics synthesized by solid state reaction route. The polycrystalline tetragonal structure of prepared ceramics was confirmed from XRD study. Analysis done using Rietveld refinement reveals reduction in lattice parameters as well as unit cell volume on substitution of Fe3+ ions in BCT lattice. Occurrence of four distinct Raman bands viz. 297 cm−1-302 cm−1, 473 cm−1-475 cm−1, 516 cm−1-524 cm−1and 729 cm−1-733 cm−1 in Raman spectroscopic studies confirms the tetragonal phase of prepared ceramic compositions which are in accordance with XRD study. The Scanning Electron Microscopy analysis revealed polyhedral shaped grains whose average grain size decreased with increase in Fe content (x) in BCT ceramics. A diffused frequency independent phase transition was observed in temperature dependent dielectric measurements. Dielectric properties improved significantly, with shifting of transition temperature, Tc close to room temperature with Fe doping. These studiessuggest applications of these ceramics in the development of environment friendly dielectric materials meeting X7R MLCCs specifications. The ferroelectric and piezoelectric properties of these ceramic compositions were found to decrease with increase in Fe concentration. Feeble room temperature ferromagnetism was observed for composition x = 0.020.

Structural and magnetic properties of RE-Al substituted nanocrystalline hexaferrites (Sr1−xRExAl2Fe10O19)

We describe the synthesis and characterization of magnetic materials with improved magnetic properties for permanent magnet applications. Sr1−xRExAl2Fe10O19 (RE = La, Ce, Tb, and Dy; x = 0.0 and 0.1) were prepared by ball milling and sintering at 1200 °C for 6 h. The effects of (Al3+–RE3+) substitution on the structural and magnetic properties of SrM hexaferrites were investigated by x-ray diffraction, scanning electron microscopy, and magnetic measurements at low (5 K), and high temperatures (from room temperature to above Curie temperature). The sample with x = 0, and that with La substitution, consisted of a single SrM phase. The rest of the samples contained traces of secondary oxide phases, and exhibited a small reduction in lattice parameters compared with the unsubstituted SrFe12O19. The coercivity of the samples (8800 ≤ HcM ≤ 9750 Oe) was more than double the standard value of the unsubstituted compound, and the Curie temperatures was >300 °C for all samples. Also, the saturation magnetization (32.5–46.4 emu g−1) was high enough to make the overall magnetic properties of these compounds potentially important for the permanent magnet industry.

Stoichiometry control in molecular beam epitaxy of BaSnO3

La-doped $\mathrm{BaSn}{\mathrm{O}}_{3}$ films were grown on $\mathrm{DySc}{\mathrm{O}}_{3}$ substrates by molecular beam epitaxy using La, Ba, and $\mathrm{Sn}{\mathrm{O}}_{2}$ sources with and without additional oxidant, respectively. Lattice parameter measurements as a function of growth conditions show a reduced lattice parameter that is likely due to substitution of $\mathrm{S}{\mathrm{n}}^{2+}$ on the Ba site. The propensity for the antisite defect is discussed as being due to the combination of oxygen-poor, Sn-rich conditions and the dual valence of Sn. Although electron mobilities are highest for films with reduced lattice parameters, antisite defects will pose an upper limit to thin film mobility. Less Sn-rich conditions lead to the formation of another defect that causes a lattice expansion. The combined effects of these defects on the lattice parameter can compensate each other and cause the appearance of a stoichiometric lattice parameter for nonstoichiometric films with poor electrical behavior.

ZnFe2O4/CuO core–shell structured nanoparticles: synthesis, structural and magnetic properties

Synthesis of core/shell structured ZnFe2O4/CuO nanoparticles with varying core diameter and different weight percentage of CuO phase [(1−x) ZnFe2O4/x CuO: x = 0.15, 0.30, 0.45 and 0.60] using double stage standard chemical co-precipitation method has been reported in this article. For first four samples only the diameter of core was varied and for other four samples only the weight percentage of CuO phase was varied. The existence of both cubic spinel ZnFe2O4 phase along with monoclinic CuO phase was verified by X-ray patterns recorded at room temperature. The average core diameter was in between 8 and 13 nm as estimated using Scherrer’s formula and further verified by HRTEM images. A reduction in lattice parameter with increasing core thickness and also with increasing CuO phase was observed. A notable enhancement in coercivity and saturation magnetization were observed in field cooled (5 T) hysteresis loops obtained at 5 K for the first four varying core diameter core–shell structured nanoparticles in comparison to bare zinc ferrite nanoparticles of almost same size. A decreasing trend in coercivity and saturation magnetization was also noticed in low temperature hysteresis loops for higher CuO content samples. A considerable improvement in blocking temperature (TB) as well as Neel temperature (TN) for all the different core diameter samples were also found in M(T) protocols. Both blocking temperature and Neel temperature decreased for increasing CuO content in composite nanoparticles. The room temperature M(H) plots exhibited superparamagnetic nature with insignificant coercivity and negligible remanence.

Operando Observations and First‐Principles Calculations of Reduced Lithium Insertion in Au‐Coated LiMn2O4

AbstractThe deposition of protective coatings on the spinel LiMn2O4 (LMO) lithium‐ion battery cathode is effective in reducing Mn dissolution from the electrode surface. Although protective coatings positively affect LMO cycle life, much remains to be understood regarding the interface formed between these coatings and LMO. Using operando powder X‐ray diffraction with Rietveld refinement, it is shown that, in comparison to bare LMO, the lattice parameter of a model Au‐coated LMO cathode is significantly reduced upon relithiation. Less charge passes through Au‐coated LMO in comparison to bare LMO, suggesting that the reduced lattice parameter is associated with decreased Li+ solubility in the Au‐coated LMO. Density functional theory calculations show that a more Li+‐deficient near‐surface is thermodynamically favorable in the presence of the Au coating, which may further stabilize these cathodes through suppressing formation of the Jahn–Teller distorted Li2Mn2O4 phase at the surface. Electronic structure and chemical bonding analyses show enhanced hybridization between Au and LMO for delithiated surfaces leading to partial oxidation of Au upon delithiation. This study suggests that, in addition to transition metal dissolution from electrode surfaces, protective coating design must also balance potential energy effects induced by charge transfer at the electrode‐coating interface.

Influence of Sn on martensitic beta Ti alloys

The influence of Sn composition in Ti-17 at% Nb alloys is studied by cyclic tension and in-situ synchrotron X-ray diffraction. It is firstly found that Sn stabilizes β-phase and effectively suppresses the formation of ω-phase. Along with β-phase stability, we observe lowering of the austenite and martensite transformation temperature by ~100 K/at% and 88 K/at%, respectively. Increasing Sn decreases the martensitic transformation strain in Ti-Nb alloys by ~1.4%/at%, larger than that in Ti-Zr-Nb-Sn systems. The influence of Sn in martensitic Ti is anisotropic: causing larger reduction in lattice parameter b and higher decreases in elastic moduli of grain families that are aligned close to the b-axis. Finally, a {013}α″, {031}α″,{122}α″ and {211}α″ quadruple texture was observed in martensitic Ti wire. At the early stage of deformation, detwinning quickly rotated {013}α″ and {211}α″ towards {031}α″ and {122}α″ components. After that, the strength of {031}α″ continued to increase, while the strength of {122}α″ texture was gradually decreased by dislocation slip as deformation continued.

Characterization of (Ti,Mo,Cr)C nanoprecipitates in an austenitic stainless steel on the atomic scale

Nanometer sized (Ti,Mo,Cr)C (MX-type) precipitates that grew in a 24% cold worked Ti-stabilized austenitic stainless steel (grade DIN 1.4970, member of the 15-15Ti austenitic stainless steels) after heat treatment were fully characterized with transmission electron microscopy (TEM), probe corrected high angle annular dark field scanning transmission electron microscopy (HR-HAADF STEM), and atom probe tomography (APT). The precipitates shared the cube-on-cube orientation with the matrix and were facetted on {111} planes, yielding octahedral and elongated octahedral shapes. The misfit dislocations were believed to have Burgers vectors a/6<112> which was verified by geometrical phase analysis (GPA) strain mapping of a matrix-precipitate interface. The dislocations were spaced five to seven atomic planes apart, on average slightly wider than expected for the lattice parameters of steel and TiC. Quantitative atom probe tomography analysis of the precipitates showed that precipitates were significantly enriched in Mo, Cr and V, and that they were hypostoichiometric with respect to C. These findings were consistent with a reduced lattice parameter. The precipitates were found primarily on Shockley partial dislocations originating from the original perfect dislocation network. These novel findings could contribute to the understanding of how TiC nanoprecipitates interact with point defects and matrix dislocations. This is essential for the application of these Ti-stabilized steels in high temperature environments or fast spectrum nuclear fission reactors.

Thermoelectric studies of Ir1−xRhxTe2 ( 0≤x≤0.3 )

We report thermoelectric properties of Ir$_{1-x}$Rh$_x$Te$_2$ ($0 \leqslant x \leqslant 0.3$) alloy series where superconductivity at low temperatures emerges as the high-temperature structural transition ($T_s$) is suppressed. The isovalent ionic substitution of Rh into Ir has different effects on physical properties when compared to the anionic substitution of Se into Te, in which the structural transition is more stable with Se substitution. Rh substitution results in a slight reduction of lattice parameters and in an increase of number of carriers per unit cell. Weak-coupled BCS superconductivity in Ir$_{0.8}$Rh$_{0.2}$Te$_2$ that emerges at low temperature ($T_c^{zero}$ = 2.45 K) is most likely driven by electron-phonon coupling rather than dimer fluctuations mediated pairing.

Effects of Alloying Elements on Thermal Expansion Behavior of Ni-Fe-Cr-Based Superalloys

The effects of alloying elements on the thermal expansion of Ni-Fe-Cr-based superalloys are investigated by optical microscope, scanning electron microscope, and transmission electron microscope. The results indicate that Fe and Cr increase the thermal expansion coefficient (TEC) of alloys and the effect of Cr on the TEC is significantly enhanced by the presence of Fe. Al and Ti present a minor influence on the TEC owing to their low contents in the alloys. The TEC of alloys rises with the reduction of lattice parameter of γ matrix in the Fe-containing or non-ferrous alloys; indeed, this is the essential reason why the TEC changes with the modification of the contents of various elements. Finally, it is found that the TEC of alloys is principally determined by the γ matrix due to its dominant amount. The γ′ phase and grain boundary also contribute to reducing the TEC, but their effects are screened by the matrix due to their negligible volume (or weight) fraction.

Optoelectronic Dichotomy of Mixed Halide CH3NH3Pb(Br1–xClx)3 Single Crystals: Surface versus Bulk Photoluminescence

In this work, the spatially dependent recombination kinetics of mixed-halide hybrid perovskite CH3NH3Pb(Br1- xCl x)3 (0 ≤ x ≤ 0.19) single crystals are investigated using time-resolved photoluminescence spectroscopy with one- and two-photon femtosecond laser excitation. The introduction of chloride by substituting a fraction of the bromide leads to a decreased lattice constant compared to pure bromide perovskite ( x = 0) and a higher concentration of surface defects. The measured kinetics under one-photon excitation (1PE) shows that increasing the chloride addition quenches the photoluminescence (PL) lifetimes, due to substitution-induced surface defects. In stark contrast, upon 2PE, the PL lifetimes measured deeper in the bulk become longer with increasing chloride addition, until the halide substitution reaches the critical concentration of ∼19%. At x = 19% Cl concentration, a significant reversal of this behavior is observed indicating a change in crystal structure beyond the continuous trends observed at lower percentages of halide substitution ( x ≤ 11%). The observed opposing trends, based on 1PE versus 2PE, highlight a dichotomy between extrinsic (surface) and intrinsic (bulk) effects of chloride substitution on the carrier dynamics in lead bromide perovskites. We discuss the physical relation between halide exchange and bulk carrier lifetimes in CH3NH3PbBr3 in terms of the Rashba effect. We propose that the latter is suppressed at the surface due to disorder in the alignment of the MA and that it increases in the bulk with Cl concentration because of the reduction in lattice parameters, which compresses the space available for the MA orientational degrees of freedom.