Study of static and dynamical properties of complex antiferroelectrics materials

The aim of this dissertation is the investigation of the static and dynamical properties of the complex antiferroelectric materials using Effective Hamiltonian method and First principles calculations. In chapter 3, a novel elemental interatomic coupling in perovskite materials which bilinearly couples the antiferroelectric displacements of cations with the rotations of the oxygen octahedra. This new coupling explains a very complex crystal structure of prototypical antiferroelectric PbZrO3. My explanation provides a unified description of many other complex antipolar crystal structures in variety of perovskite materials, including the occurrence of incommensurate phases in some of them. In chapter 4, results and analysis of atomistic simulations explaining the dynamics of antiferroelectric distortions in BiFeO3 (BFO) bulk under hydrostatic pressure are reported. This system undergoes a phase transition on cooling from paraelectric Pm3 ̄m state at high temperatures to an intermediate P4/mbm phase followed by Pnma state at low temperatures. On the basis of my calculations, I prepared an analytical model of these phase transitions. The model developed can be easily applied to predict dynamics of antipolar cation motion in improper ferroelectrics. I found out that the antipolar modes do not soften themselves in the high temperature regime but they soften in the intermediate and Pnma phases, due to trilinear energetic coupling term. In chap- ter 5, the finite temperature behavior of the polar, antipolar, and antiferrodistortive phonons in a prototypical hybrid improper ferroelectric (BiFeO3)1/(NdFeO3)1 1:1 superlattice is studied. In the low-temperature phase, a spontaneous polarization appears due to trilinear coupling of structural and antiferroelectric (ferrroelectric) modes. In chapter 6, results of first-principles calculations to investigate and analyze properties of (001) thin films made of the most complex perovskite system, namely NaNbO3, are presented.Ferroelectric, antiferroelectric and antiferrodistortive properties of this thin film are reported and discussed, as a function of misfit strain

Analisis Pengaruh Kecerdasan Emosional dan Keseimbangan Kehidupan Kerja

The study aimed to analyze the relationship between emotional intelligence on employee engagement, job satisfaction, and work-life balance. In addition, analyze the relationship of work-life balance on employee engagement, job satisfaction, and job performance, as well as the effect of performance on career development for employees of one of the world-class tire supplier companies in Suryacipta Industrial Estate, Karawang. The data processing method used structural equation modeling (SEM). The results showed that there is a significant effect of emotional intelligence on employee engagement and work-life balance, but does not have a significant effect on job satisfaction. Work-life balance also has a significant effect on employee engagement, job satisfaction, and job performance. In addition, job performance has a significant effect on career development. The work-life balance of employees needs to be considered by the organization so that employees can carry out two very different roles effectively to increase job performance. Future research is expected to be able to use a more specific questionnaire statement on emotional intelligence variables so that it can provide more representative results

A new look at the temperature-dependent properties of the antiferroelectric model PbZrO3: an effective Hamiltonian study

A novel atomistic effective Hamiltonian scheme, incorporating an original and simple bilinear energetic coupling, is developed and used to investigate the temperature dependent physical properties of the prototype antiferroelectric PbZrO3 (PZO) system. This scheme reproduces very well the known experimental hallmarks of the complex Pbam orthorhombic phase at low temperatures and the cubic paraelectric state of Pm 3m symmetry at high temperatures. Unexpectedly, it further predicts a novel intermediate state also of Pbam symmetry, but in which anti-phase oxygen octahedral tiltings have vanished with respect to the Pbam ground state. Interestingly, such new state exhibits a large dielectric response and thermal expansion that remarkably agree with previous experimental observations and the x-ray experiments we performed. We also conducted direct first-principles calculations at 0K which further support such low energy phase. Within this fresh framework, a re-examination of the properties of PZO is thus called for.Comment: 21 pages, 4 figures. This paper is submitted to Physical Review

The Effect of Authentic Leadership on Organizational Citizenship Behavior: The Role of Psychological Empowerment and Quality of Working Life

Objective: This study aims to investigate the influence of authentic leadership on organizational citizenship behavior (OCB) and examine the role of psychological empowerment and quality of working life (QWL) as mediation in the construction of proposed relationships. Design/Methods/Approach: This study adopts a quantitative method by conducting cross-sectional surveys of multi-sectoral employees in Jakarta, and Surabaya, resulting in 271 respondents. The collected data were analyzed using structural equation models with SmartPLS 3.0 and tested with hierarchical component models or second-order constructs. Findings: The findings of this study show that QWL and psychological empowerment are important variables in mediating the effects of authentic leadership to encourage employees to be willing to demonstrate OCB in the work environment. Originality/Value: This study contributes to the existing literature by investigating the role of psychological empowerment and QWL mediation variables in mediating the indirect influence of authentic leadership on OCB in the Indonesian context. The findings from this study provide theoretical insights and practical implications for authentic leadership in organizations, as well as the foundation for continuous research into QWL and psychological empowerment that may have a solid direct influence and full mediation role on employees’ OCB. Practical/Policy implication: Given the results, human resource managers must try their best to fulfill aspects of the quality of working life and increase employee psychological empowerment. Because both variables play an important role in determining the positive effect of authentic leadership on the OCB of employees in the organizatio

Adenine Methylation in Drosophila Is Associated with the Tissue-Specific Expression of Developmental and Regulatory Genes

N6-methyladenine (6mA or m6dA) is a DNA modification that has long been known to play an important role in a variety of biological functions in prokaryotes. This modification has only recently been described in eukaryotes, where it seems to have evolved species-specific functions ranging from nucleosome positioning to transposon repression. In Drosophila, 6mA has been shown to be important for enforcing the tissue specificity of neuronal genes in the brain and suppressing transposable element expression in the ovaries. In this study, we have analyzed the raw signal data from nanopore sequencing to identify 6mA positions in the D. melanogaster genome at single-base resolution. We find that this modification is enriched upstream from transcription start sites, within the introns and 3′ UTRs of genes, as well as in simple repeats. These 6mA positions are enriched for sequence motifs that are recognized by known transcriptional activators involved in development, such as Bicoid and Caudal, and the genes that carry this modification are enriched for functions involved in development, regulation of transcription, and neuronal activity. These genes show high expression specificity in a variety of tissues besides the brain, suggesting that this modification may play a more general role in enforcing the specificity of gene expression across many tissues, throughout development, and between the sexes

Energetic Couplings in Ferroics

International audienceFerroics include diverse degrees of freedom (such as structural distortions and magnetic moments) among which cross couplings occur, rendering a large variety of interesting phenomena. Determining such couplings, based on symmetry analysis, is not only important to interpret observed phenomena but can also result in novel predictions to be then experimentally checked. Often, such energetic couplings are difficult to construct without a deep knowledge of group theoretical symmetry principles. In the present review, a crash course towards the derivation of energetic couplings, without using much the group theoretical language, is provided. Rather, the present approach relies on a graphical technique and suitable symbolic language, which naturally yields some known couplings (resulting in, e.g., spin/dipole canting, magnetically driven polarization and antipolar/antiferroelectric states). This review also reports and discusses other symmetry-allowed energetic terms, including some leading to the occurrence of an electric polarization in a variety of materials, and "exotic" ones that generate complex phases and phenomena in, e.g., nanostructures and heterostructures

Temperature-dependent properties of the antiferroelectric model PbZrO 3 : An effective Hamiltonian study

International audienceA novel atomistic effective Hamiltonian scheme, incorporating an original and simple bilinear energetic coupling, is developed and used to investigate the temperature dependent physical properties of the prototype antiferroelectric PbZrO 3 (PZO) system. This scheme reproduces very well the known experimental hallmarks of the complex Pbam orthorhombic phase at low temperatures and the cubic paraelectric state of Pm 3m symmetry at high temperatures. Unexpectedly, it further predicts a novel intermediate state also of Pbam symmetry, but in which anti-phase oxygen octahedral tiltings have vanished with respect to the Pbam ground state. Interestingly, such new state exhibits a large dielectric response and thermal expansion that remarkably agree with previous experimental observations and the x-ray experiments we performed. We also conducted direct first-principles calculations at 0K which further support such low energy phase. Within this fresh framework, a re-examination of the properties of PZO is thus called for