A theoretical investigation of the lead-free double perovskites halides Rb2 XCl6 (X = Se, Ti) for optoelectronic and thermoelectric applications.

In this study, structural, electronic, optical, thermoelectric, and thermodynamics properties of vacancy-ordered double perovskites Rb2 XCl6 (X = Se, Ti) were explored theoretically. The results revealed that Rb2SeCl6 and Rb2 TiCl6 are indirect band gap (Eg ) semiconductors with Eg values of 2.95 eV, and 2.84 eV respectively. The calculated properties (phonons, elastic constant, Poisson's ratio, and Pugh's ratio) revealed that both materials are dynamically and chemically stable and can exhibit brittle (Rb2 SeCl6 ) and ductile (Rb2 TiCl6 ) nature. From the analysis of optical parameters, it was noticed that the refractive index of the materials has a value of 1.5-2.0 where light absorption was found from the visible to the ultraviolet region. The thermoelectric properties determined by using the BoltzTrap code demonstrated that at room temperature, the Figure of merit (ZT) was found to be 0.74 and 0.76 for Rb2 SeCl6 and Rb2 TiCl6 , respectively. Despite a moderate value of ZT in such materials, further studies might explore effective methods for tuning the electronic band gap and improving the thermoelectric response of the material for practical energy production applications.

Sn3C2monolayer with transition metal adatom for gas sensing: a density functional theory studies.

The gas sensing properties of pristine Sn3C2monolayer and different transition metal adatom (TM-Sn3C2, where TM = Fe, Co, Ni, Cu, Ru, Rh, Pd and Ag) was investigated using van der Waals corrected density functional theory. The understanding and potential of use of Sn3C2monolayers as sensors or adsorbent for CO, CO2, NO, NO2and SO2gaseous molecules is evaluated by calculating the adsorption and desorption energetics. From the calculated adsorption energies, we found that the pristine Sn3C2monolayer and 3dTM has desirable properties for removal of the considered molecules based on their high adsorption energy, however the 4dTM is applicable as recoverable sensors. We applied an Arrhenius-type equation to evaluate the recovery time for the desorption of the molecules on the pristine and TM adatom on Sn3C2monolayer. We found that the negative adsorption energies from -1 to -2 eV of the molecules resulted in easier recovery of the adsorbed gases at reasonable temperatures compared to adsorption energies in between 0 and -1 eV (weakly physiosorbed) and below -2 eV (strongly chemisorbed). Hence, we obtained that the Rh-Sn3C2, Ru-Sn3C2, Pd-Sn3C2, Pd-Sn3C2, and Rh-Sn3C2monolayers are good recoverable scavengers for the CO, CO2, NO, NO2, and SO2molecules. The current theoretical calculations provide new insight on the effect of TM adatoms on the structural, electronic, and magnetic properties of the Sn3C2monolayer and different transition metal adatom as well as shed light on their application as gas sensors/scavengers.

Electronic, magnetic, vibrational, and X-ray spectroscopy of inverse full-Heusler Fe2IrSi alloy.

We report the electronic, magnetic, structural, vibrational, and X-ray absorption spectroscopy of the inverse full-Heusler Fe2IrSi alloy. We employed state-of-the-art first-principles computational techniques. Our ab initio calculations revealed a ferromagnetic half-metallicity with a magnetic moment of ∼5.01 µB, which follows the Slater Pauling rule. We show rich magnetic behavior due to spin-orbit coupling through the entanglement of the Fe-3d/Ir-5d orbitals. The large extension of the Ir-5d orbital and the itinerant Fe-3d states enhanced spin-orbit and electron-electron interactions, respectively. The analyses of our results reveal that electron-electron interactions are essential for the proper description of the electronic properties while spin-orbit coupling effects are vital to accurately characterize the X-ray absorption and X-ray magnetic circular dichroism spectra. We estimate the strength of the spin-orbit coupling by comparing the intensity of the white-line features at the L3 and L2 absorption edges. This led to a branching ratio that deviates strongly from the statistical ratio of 2, indicative of strong spin-orbit coupling effects in the inverse full-Heusler Fe2IrSi alloy.

Membrane softening by nonsteroidal anti-inflammatory drugs investigated by neutron spin echo.

In spite of their well-known side effects, the nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most commonly prescribed medications for their antipyretic and anti-inflammatory actions. Interaction of NSAIDs with the plasma membrane plays a vital role in their therapeutic actions and defines many of their side effects. In the present study, we investigate the effects of three NSAIDs, aspirin, ibuprofen, and indomethacin, on the structure and dynamics of a model plasma membrane using a combination of small angle neutron scattering (SANS) and neutron spin echo (NSE) techniques. The SANS and NSE measurements were carried out on a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane, with and without NSAIDs, at two different temperatures, 11 °C and 37 °C, where the DMPC membrane is in the gel and fluid phase, respectively. SANS data analysis shows that incorporation of NSAIDs leads to bilayer thinning of the membrane in both the phases. The dynamic properties of the membrane are represented by the intermediate scattering functions for NSE data, which are successfully described by the Zilman and Granek model. NSE data analysis shows that in both gel and fluid phases, addition of NSAIDs results in a decrease in the bending rigidity and compressibility modulus of the membrane, which is more prominent when the membrane is in the gel phase. The magnitude of the effect of NSAIDs on the bending rigidity and compressibility modulus of the membrane in the gel phase follows an order of ibuprofen > aspirin > indomethacin, whereas in the fluid phase, it is in the order of aspirin > ibuprofen > indomethacin. We find that the interaction between NSAIDs and phospholipid membranes is strongly dependent on the chemical structure of the drugs and physical state of the membrane. Mechanical properties of the membrane can be quantified by the membrane's bending rigidity. Hence, the present study reveals that incorporation of NSAIDs modulates the mechanical properties of the membrane, which may affect several physiological processes, particularly those linked to the membrane curvature.

Therapeutic Drug Monitoring of Antiepileptic Drugs at a Tertiary Care Hospital of Eastern Nepal.

Background Therapeutic drug monitoring (TDM) is the process of measuring drug level in body fluids. It is done to maintain plasma concentration of the drug under therapy within a specific target range for maximum therapeutic efficacy without unnecessary exposure to adverse effects. Objective This study aims to evaluate necessity of therapeutic drug monitoring in Phenytoin, Carbamazepine and Lamotrigine therapy among epileptic patients. Method A prospective, cross-sectional study was conducted for a period of one year at BP Koirala Institute of Health Sciences, Dharan, Nepal. After taking detailed history, blood samples were collected from epileptic patients on monotherapy with the selected drugs. Plasma levels of these drugs were analyzed using High Performance Liquid Chromatography technique (HPLC). Out of total 42 selected patients, 21 were tested for phenytoin, 17 for carbamazepine and four for lamotrigine. The result was categorized into therapeutic, sub-therapeutic and above-therapeutic groups based on reference range. Result Out of total 21 samples tested for phenytoin, 15(71.4%) had plasma drug level within therapeutic range, 5(23.8%) had within subtherapeutic range and 1(4.8%) had above therapeutic range. Analysis of carbamazepine plasma level showed 14(82.3%) at therapeutic level, 1(5.9%) at sub-therapeutic level and 2(11.8%) at above-therapeutic level. Lamotrigine testing in four samples showed 2(50% in) both within therapeutic range and above-therapeutic range. Conclusion Therapeutic drug monitoring of phenytoin, carbamazepine and lamotrigine showed variation in plasma level irrespective of the therapeutic dose. It is suggested that dose adjustment of antiepileptic drugs should be done after establishing 'individual therapeutic range' following regular plasma monitoring.

Anatomy-based definition of point A utilizing three-dimensional volumetric imaging approach for high-dose-rate (HDR) intracavitary brachytherapy dose prescription when treating cervical cancer using limited resources.

This study was designed to determine whether volumetric imaging could identify consistent alternative prescription methods to Manchester/point A when prescribing radiation dose in the treatment of cervical cancer using HDR intracavitary brachy-therapy (ICBT). One hundred and twenty-five treatment plans of 25 patients treated for carcinoma of the cervix were reviewed retrospectively. Each patient received 5 fractions of HDR ICBT following initial cisplatin-based pelvic chemoradiation, and radiation dose was originally prescribed to point A (ICRU-38). The gross tumor volume (GTV) and high-risk clinical target volume (HR-CTV) were contoured in three dimensions on the CT datasets, and inferior-superior, anterior-posterior, and left-right dimensions HR-CTV were recorded along with multiple anatomic and skeletal dimensions for each patient. The least square-best fit regression lines were plotted between one half of the HR-CTV width and pelvic cavity dimension at femoral head level and at maximum cavity dimension. The points in both plots lie reasonably close to straight lines and are well defined by straight lines with slopes of 0.15 and 0.17; intercept on y-axes of -0.08 and -0.03, point A, at the same level as defined based on applicator coordinates, is defined using this correlation, which is a function of distance between femoral heads/dimensions of maximum pelvic cavity width. Both relations, defined by straight lines, provide an estimated location of point A, which provides adequate coverage to the HR-CTV compared to the point A defined based on applicator coordinates. The point A defined based on femoral head distance would, therefore, be a reasonable surrogate to use for dose prescription because of subjective variation of cavity width dimension. Simple surrogate anatomic/skeletal landmarks can be useful for prescribing radiation dose when treating cervical cancer using intracavitary brachytherapy in limited-resource settings. Our ongoing work will continue to refine these models.

Estimated verbal IQ and the odds of problem gambling: a population-based study.

BACKGROUND: The neurocognitive deficits and other correlates of problem gambling are also observable in individuals with lower cognitive abilities, suggesting that a low IQ may be a determinant of problem gambling. There has been very little research into this possibility. This study aimed to investigate the characteristics associated with problem gambling in a large population-based study in England, with a particular focus on IQ. METHOD: The Adult Psychiatric Morbidity Survey (APMS) 2007 comprised detailed interviews with 7403 individuals living in private households in England. Problem gambling was ascertained using a questionnaire based on DSM-IV criteria. Verbal IQ was estimated using the National Adult Reading Test (NART). Confounders included socio-economic and demographic factors, common mental disorders, impulsivity, smoking, and hazardous drug and alcohol use. RESULTS: More than two-thirds of the population reported engaging in some form of gambling in the previous year, but problem gambling was rare [prevalence 0.7%, 95% confidence interval (CI) 0.5-1.0]. The odds of problem gambling doubled with each standard deviation drop in estimated verbal IQ [adjusted odds ratio (OR) 2.1, 95% CI 1.3-3.4, p = 0.003], after adjusting for other characteristics associated with problem gambling including age, sex, socio-economic factors, drug and alcohol dependence, smoking, impulsivity and common mental disorders. There was no strong relationship observed between IQ and non-problem gambling. CONCLUSIONS: People with lower IQs may be at a higher risk of problem gambling. Further work is required to replicate and study the mechanisms behind these findings, and may aid the understanding of problem gambling and inform preventative measures and interventions.

Paneer-An Indian soft cheese variant: a review.

Paneer, a popular indigenous dairy product of India, is similar to an unripened variety of soft cheese which is used in the preparation of a variety of culinary dishes and snacks. It is obtained by heat and acid coagulation of milk, entrapping almost all the fat, casein complexed with denatured whey proteins and a portion of salts and lactose. Paneer is marble white in appearance, having firm, cohesive and spongy body with a close-knit texture and a sweetish-acidic-nutty flavour. Preparation of paneer using different types of milk and varied techniques results in wide variation in physico-chemical, microbiological and sensory quality of the product. Paneer blocks of required size are packaged in laminated plastic pouches, preferably vacuum packaged, heat sealed and stored under refrigeration. Paneer keeps well for about a day at ambient temperature and for about a week under refrigeration (7 °C). The spoilage of paneer is mainly due to bacterial action. Successful attempts have been made to enhance the shelf life of paneer. This review deals with the history, method of manufacture, factors affecting the quality, physico-chemical changes during manufacture, chemical composition and nutritional profile, packaging and shelf life of paneer.

Comprehensive investigation of structural, magnetic, electronic, optical, mechanical, and piezoelectric properties of ATiO3 (A= Mn, Fe, Ni) compounds for sustainable energy materials.

This work employs Density Functional Theory (DFT) to investigate the characteristics of ATiO3 (A= Mn, Fe, Ni) by utilizing GGA and DFT+U formalisms. Our results reveal that the investigated compounds exhibit a ground-state magnetic arrangement in the G-type antiferromagnetic configuration. Substitution of the A-site atoms along the row leads to a decrease in volume due to poor electronic shielding effects with transition metals. All systems investigated are stable under dynamical conditions, with no imaginary phonon. From the formation energy calculations, NiTiO3 was identified as the most formable and stable compound. DFT+U was most effective for FeTiO3, resulting in significantly wider bandgaps compared to the GGA-level bandgaps. Optical properties such as static dielectric constants, refractive index, and reflectivity were overestimated by the GGA when compared to DFT+U results. The absorption edges of FeTiO3, MnTiO3, and NiTiO3 were analyzed, with DFT+U showing delayed onset compared to GGA. FeTiO3 was found to be the most effective absorber within the visible spectrum according to DFT+U, while NiTiO3 was predicted to be the best absorber by GGA. Each compound's mechanical stability was tested and verified based on the Born criteria, with FeTiO3 exhibiting the highest elastic moduli under DFT+U, while NiTiO3 had the highest shear and Young's modulus according to GGA. Among the studied compounds, FeTiO3 is the best-performing and most efficient piezoelectric compound with e_16 = 5.418 C m^(-2) under DFT+U. Overall, the studied compounds demonstrate promising capabilities for a wide range of applications in the field of photovoltaic devices, and piezoelectric materials, due to their remarkable optical, and piezoelectric properties.

Hybrid-DFT study of halide perovskites, an energy-efficient material under compressive pressure for piezoelectric applications.

Recent studies have reported that lead-halide perovskites are the most efficient energy-harvesting materials. Regardless of their high-output energy and structural stability, lead-based products have risk factors due to their toxicity. Therefore, lead-free perovskites that offer green energy are the expected alternatives. We have taken CsGeX3(X = Cl, Br, and I) as lead-free halide perovskites despite knowing the low power conversion rate. Herein, we have tried to study the mechanisms of enhancement of energy-harvesting capabilities involving an interplay between structure and electronic properties. A density functional theory simulation of these materials shows a decrease in the band gaps, lattice parameters, and volumes with increasing applied pressure. We report the high piezoelectric responses and high electro-mechanical conversion rates, which are intriguing for generating electricity through mechanical stress.

Sleep disturbances and depressive symptoms: an investigation of their longitudinal association in a representative sample of the UK general population.

BACKGROUND: It has been argued that sleep disturbances are a risk factor for depression but previous longitudinal studies have had limitations and not addressed alternative explanations. The aim of this study was to examine the longitudinal association between sleep disturbances and depressive symptoms in a nationally representative sample. METHOD: Data from the 18-month follow-up of the UK National Psychiatric Morbidity survey were used (n = 2406). Sleep disturbances, depressive and other psychiatric symptoms (fatigue, concentration problems, irritability, anxiety and pain symptoms) were assessed using the Revised Clinical Interview Schedule (CIS-R). The bidirectional association between symptoms was investigated with logistic regression analyses and path analysis. RESULTS: Sleep disturbances and depressive symptoms were correlated with each other cross-sectionally (r = 0.52, p < 0.001). In the longitudinal analysis, sleep disturbances at baseline did not predict depressive symptoms at follow-up [odds ratio (OR) 1.27, 95% confidence interval (CI) 0.51-3.19] and the same was observed for the reciprocal association (OR 0.87, 95% CI 0.56-1.35). In the path analysis, the reciprocal model did not have a better fit compared to the simpler first-order model without cross-lagged paths. The path from sleep disturbances at baseline to depressive symptoms at follow-up had a minimal contribution to the explained variance of the latter (<1%). CONCLUSIONS: Previous studies may have overestimated the importance of sleep disturbances as an independent risk factor of depression. The strong cross-sectional association is compatible with sleep disturbances being either a prodromal or a residual symptom of depression and this may have implications for recognition and treatment of depression.

The population impact of common mental disorders and long-term physical conditions on disability and hospital admission.

BACKGROUND: Long-term physical conditions (LTCs) consume the largest share of healthcare budgets. Although common mental disorders (CMDs) and LTCs often co-occur, the potential impact of improved mental health treatment on severe disability and hospital admissions for physical health problems remains unknown. Method A cross-sectional study of 7403 adults aged 16-95 years living in private households in England was performed. LTCs were ascertained by prompted self-report. CMDs were ascertained by structured clinical interview. Disability was assessed using questions about problems with activities of daily living. Population impact and potential preventive gain were estimated using population-attributable fraction (PAF), and conservative estimates were obtained using 'treated non-cases' as the reference group. RESULTS: Of the respondents, 20.7% reported at least one LTC. The prevalence of CMDs increased with the number of LTCs, but over two-thirds (71.2%) of CMD cases in people with LTCs were untreated. Statistically significant PAFs were found for CMDs and recent hospital admission [13.5%, 95% confidence intervals (CI) 6.6-20.0] and severe disability (31.3%, 95% CI 27.1-35.2) after adjusting for LTCs and other confounders. Only the latter remained significant when using the most conservative estimate of PAF (21.8%, 95% CI 14.0-28.9), and this was reduced only slightly when considering only participants with LTCs (18.5%, 95% CI 7.9-27.9). CONCLUSIONS: Better treatments for CMDs in people with LTCs could achieve almost the same population health gain in terms of reducing severe disability as those targeted at the entire population. Interventions to reduce the prevalence of CMDs among people with LTCs should be part of routine medical care.

The relationship between happiness and intelligent quotient: the contribution of socio-economic and clinical factors.

BACKGROUND: Happiness and higher intelligent quotient (IQ) are independently related to positive health outcomes. However, there are inconsistent reports about the relationship between IQ and happiness. The aim was to examine the association between IQ and happiness and whether it is mediated by social and clinical factors. Method The authors analysed data from the 2007 Adult Psychiatric Morbidity Survey in England. The participants were adults aged 16 years or over, living in private households in 2007. Data from 6870 participants were included in the study. Happiness was measured using a validated question on a three-point scale. Verbal IQ was estimated using the National Adult Reading Test and both categorical and continuous IQ was analysed. RESULTS: Happiness is significantly associated with IQ. Those in the lowest IQ range (70-99) reported the lowest levels of happiness compared with the highest IQ group (120-129). Mediation analysis using the continuous IQ variable found dependency in activities of daily living, income, health and neurotic symptoms were strong mediators of the relationship, as they reduced the association between happiness and IQ by 50%. CONCLUSIONS: Those with lower IQ are less happy than those with higher IQ. Interventions that target modifiable variables such as income (e.g. through enhancing education and employment opportunities) and neurotic symptoms (e.g. through better detection of mental health problems) may improve levels of happiness in the lower IQ groups.

First-principles investigation of the electronics, optical, mechanical, thermodynamics and thermoelectric properties of Na based Quaternary Heusler alloys (QHAs) NaHfXGe (X = Co, Rh, Ir).

In this study, we explored the electronic and thermoelectric (TE) properties of the Na-based Quaternary Heusler Alloys (QHAs) NaHfXGe (X = Co, Rh, Ir) using density functional theory (DFT). We performed the spin-polarized DFT calculations at the general gradient approximation (GGA) level and confirmed the ground state non-magnetic configuration of NaHfXGe. The mechanical and thermodynamical stabilities are analyzed and discussed to validate the stability by calculating the elastic constant and phonon dispersion curve. A thorough investigation on the electronic properties are carried out by performing the GGA, GGA+U, and GGA+SOC formalism where we report the semi-conducting characteristic of NaHfCoGe and NaHfRhGe QHAs. However, NaHfIrGe is predicted to be a non-magnetic metal. From the calculated optical properties we found that the most active optical absorption occurs within the vis-UV region withα>105 cm-1, therefore the studied QHAs are proposed to be a promising optoelectronic materials. The results of the thermodynamic properties have shown that NaHfXGe follows Debye's low-temperature specific heat law and the classical thermodynamics of the Dulong-Petit law at high temperatures. The calculated TE efficiency using GGA+SOC formalism atT= 1200 K are ZT∼1.22 and 0.57 for NaHfCoGe and NaHfRhGe, suggesting that these materials are potential TE materials to operate at high temperature.

Light-into-heat conversion in La2O3:Er(3+)-Yb3+ phosphor: an incandescent emission.

Low-power-threshold cw laser-induced incandescence (CWLII) has been observed in La(2)O(3):Er(3+)-Yb(3+) phosphor on excitation by a 976 nm IR laser. It is suggested that incandescence originates from the extensive heating induced by the nonradiative processes taking place following the laser excitation. Other mechanisms for similar observations have also been suggested in the literature and have been discussed with the present observations. The estimated temperature for the CWLII approaches around 2650 K, and this seems to provide an effective way to rapidly attain high temperature in nano/microvolumes of phosphor. The phosphor exhibited efficient upconversion, and the ratio of the (2)H(11/2)→(4)I(15/2) and (4)S(3/2)→(4)I(15/2) band intensities of Er(3+) permits measurement of the temperature rise, from a distance.

In-vitro carbofuran induced micronucleus formation in human blood lymphocytes.

The farmers in general get exposed to different chemicals including pesticides. Many of these compounds are capable of inducing mutations in DNA and lead to several diseases including cancer. Carbofuran is a broad spectrum pesticide and frequently used in agricultural practices in India. In this study we intended to evaluate DNA damage inflicted by pesticide exposure in human blood lymphocytes under in vitro condition. The lymphocytes were exposed to varying concentrations of carbofuran (0—50μM) and analyzed by means of the micronucleus (MN) test. The results obtained showed significant increase in MN frequency after exposure to 5, 10, 25 and 50μM of carbofuran as compared to the control group. The frequencies of MN were observed to be in concentration dependent manner. As we further increase the concentration of carbofuran, we observed significant decrease in the mean percentage of binucleated cells (70—49%) and increase in the number of micronuclei formed per 1000 binucleated cells. Simultaneously, we also observed reduction in Cytokinesis—Block Proliferation index (CBPI) with increase in the carbofuran concentrations. The results indicate that this pesticide may exhibit genotoxic effect at higher concentrations. This study emphasizes the need to reinforce the good practices campaigns in order to enlighten those who work with pesticides and also to make them aware about the importance of using protective measures.

Quantitative investigations of aggregate systems.

Nanomaterials with disordered, ramified structure are increasingly being used for applications where low cost and enhanced performance are desired. A particular example is the use in printed electronics of inorganic conducting and semiconducting nanoparticles. The electrical, as well as other physical properties depend on the arrangement and connectivity of the particles in such aggregate systems. Quantification of aggregate structure and development of structure/property relationships is difficult and progress in the application of these materials in electronics has mainly been empirical. In this paper, a scaling model is used to parameterize the structure of printed electronic layers. This model has chiefly been applied to polymers but surprisingly it shows applicability to these nanolayers. Disordered structures of silicon nanoparticles forming aggregates are investigated using small angle x-ray scattering coupled with the scaling model. It is expected that predictions using these structural parameters can be made for electrical properties. The approach may have wide use in understanding and designing nano-aggregates for electronic devices.

Physico-chemical quality parameters and overall quality index of apple during storage.

Physico-chemical quality parameters of apple were measured during storage using standard techniques and fitted to model expressions for developing an overall quality index (Iq). Predicted Iq was validated with the trends of sensory scores. Total Soluble Solids (TSS) and acidity varied from 13.2 to 12.3 ºBrix and 0.161 to 0.079%, respectively whereas, Hunter colour values L, a, b and yellowness index were 48.7-56.1, 11.0-19.4, 18.8-20.2 and 84.6-98.2, respectively. The gloss at 45 and 60º incidence angles, density and Iq varied from 7.5 to 4.3 and 6.7 to 2.6 GU, 1.01 to 0.96 kg m(-3) and 0.26 to 1.02, respectively. The variation in sensory overall quality scores with storage period was found to be in line with computed overall quality index. The Iq thus, could be defined as the ratio of product of acidity and TSS to the mode of product of a and b Hunter colour values. The polynomial regression equations for Iq with TSS, acidity, a, b, and storage period yielded the correlation coefficients of 0.8443, 0.9838, 0.7130, 0.7183 and 0.9665, respectively; which indicated that overall quality index could be predicted nondestructively using any one of these parameters during storage.

Electronic, mechanical, optical and piezoelectric properties of glass-like sodium silicate (Na2SiO3) under compressive pressure.

The structural, mechanical, electronic, optical and piezoelectric properties of Na2SiO3 are studied under varying compressive unidirectional pressure (0-50 GPa with a difference of 10 GPa) using density functional theory (DFT). The calculated structural properties agree well with previously reported results. At 12 GPa, our calculation shows a structural phase transition from orthorhombic Cmc21 to triclinic P1. The mechanical profile of Na2SiO3 structures under different compressive unidirectional pressures are analysed by calculating the elastic moduli, Poisson's ratio and eigenvalues of stiffness matrix. Our study shows the mechanical stability of the system up to a pressure of 40 GPa. Herein, we have obtained an indirect band gap of 2.97 eV at 0 GPa. Between 0-50 GPa, the band gaps are within the range 2.62 to 3.46 eV. The system in our study possesses a wide band gap and high optical absorption in the UV-Vis range of electromagnetic radiation. The calculated static refractive indices η x,y,z (0) are close to unity suggesting its transparency. For piezoelectric properties, we have reported the total Cartesian polarization. Our calculations have revealed that Na2SiO3 is a promising candidate for optoelectronic devices while its application in ferroelectric and piezoelectric devices could be improved with further research.

Electronic, mechanical and piezoelectric properties of glass-like complex Na2Si1-x Ge x O3 (x = 0.0, 0.25, 0.50, 0.75, 1.0).

Motivated by our previous work on pristine Na2SiO3, we proceeded with calculations on the structural, electronic, mechanical and piezoelectric properties of complex glass-like Na2Si1-x Ge x O3 (x = 0.0, 0.25, 0.50, 0.75, 1.0) by using density functional theory (DFT). Interestingly, the optimized bond lengths and bond angles of Na2SiO3 and Na2GeO3 resemble each other with high similarity. On doping we report the negative formation energy and feasibility of transition of Na2SiO3 → Na2GeO3 while the structural symmetry is preserved. Analyzing the electronic profile, we have observed a reduced band gap on increasing x = Ge concentration at Si-sites. All the systems are indirect band gap (Z-Γ) semiconductors. The studied systems have shown mechanical stabilities by satisfying the Born criteria for mechanical stability. The calculated results have shown highly anisotropic behaviour and high melting temperature, which are a signature of glass materials. The piezoelectric tensor (both direct and converse) is computed. The results thus obtained predict that the systems under investigation are potential piezoelectric materials for energy harvesting.