Thermal effects on CH3_3NH3_3PbI3_3 perovskite from ab-initio molecular dynamics simulations

We present a molecular dynamics simulation study of CH$_3$NH$_3$PbI$_3$ based on forces calculated from density functional theory. The simulation were performed on model systems having 8 and 27 unit cells, and for a total simulation time of 40 ps in each case. Analysis of the finite size effects, in particular the mobility of the organic component, suggests that the smaller system is over correlated through the long range electrostatic interaction. In the larger system this finite size artifact is relaxed producing a more reliable description of the anisotropic rotational behavior of the methyl ammonium molecules. The thermal effects on the optical properties of the system were also analyzed. The HOMO-LUMO energy gap fluctuates around its central value with a standard deviation of approximately 0.1 eV. The projected density of states consistently place the Fermi level on the $p$ orbitals of the I atoms, and the lowest virtual state on $p$ orbitals of the Pb atoms throughout the whole simulation trajectory.Comment: 16 pages, 11 figure

The extent to which Palestinian schoolchildren adhere to the principles of human rights from the point of view of teachers

من خلال معايشة الواقع الفلسطيني، يلحظ بشكل جلي أن هناك استهداف مباشر للشباب الفلسطيني في جميع مجالات الحياة الصحية والنفسية والتعليمية والاجتماعية. هدفت هذه الدراسة الكشف عن مدى التزام المدارس الفلسطينية بمبادئ حقوق الإنسان للطلبة من المدارس الفلسطينية، ولتحقيق أهداف الدراسة تم تصميم استبيان مكون من (25) فقرة، وتم التحقق من صدق الأداة بعرضها على مجموعة من المحكمين من ذوي الخبرة، أما بخصوص معامل الثبات فقد تم حسابه باستعمال اختبار كرونباخ ألفا وقد بلغ (0.94)، تم توزيعها على (214) معلم ومعلمة خلال الفصل الدراسي الثاني من العام الدراسي (2017/2018م)، وبعد إجراء العمليات الإحصائية المناسبة تبين أن المتوسط الحسابي للدرجة الكلية كان متوسطاً عند الطلبة حيث بلغ (3.2) من (5.0) وبنسبة (%64).Through the experience of the Palestinian reality, it is clear that there is a direct targeting of Palestinian youth in all areas of health, psychological, educational and social life. The aim of this study was to determine the extent to which Palestinian schools adhere to the principles of human rights for students from Palestinian schools. To achieve the objectives of the study, a questionnaire was constructed consisting of (25) paragraphs. The tool was verified by presenting it to a group of experienced arbitrators. (0.94), distributed to (214) teachers during the second semester of the academic year (2017/2018). After conducting the appropriate statistical operations, it was found that the mean of the total score was average among the students, 3.2) from (5.0) and by (64%)

The role of human resources in the development of the performance of Palestinian private schools’ employees from the perspective of the workers themselves

هدفت هذه الدراسة إلى التعرف على دور الموارد البشرية في تطور أداء العاملين بالمدارس الخاصة الفلسطينية من وجهة نظر العاملين أنفسهم، وعليه فان هذه الدراسة تحاول الإجابة عن الأسئلة التالية: ما دور الموارد البشرية في تطور أداء العاملين بالمدارس الخاصة الفلسطينية من وجهة نظر العاملين أنفسهم؟ هل تختلف استجابات عينة الدراسة نحو دور الموارد البشرية في تطور أداء العاملين بالمدارس الخاصة الفلسطينية من وجهة نظر العاملين أنفسهم تبعاً للمتغيرات الآتية (التخصص، والنوع الاجتماعي، وسنوات الخبرة، والعمر)؟ وتكون مجتمع الدراسة من عينة قوامها (100) من مدراء المدارس الخاصة الفلسطينية خلال الفصل الثاني من العام الدراسي (2018/2019م). وتم اختيار العينة بطريقة عشوائية.This study aims to identify the role of human resources in the development of the performance of Palestinian private schools’ employees from the point of view of the employees themselves. Therefore, this study attempts to answer the following questions: - What is the role of human resources in the development of the performance of Palestinian private school workers from the point of view of the workers themselves? - Do the responses of the study sample differ from the perspective of the employees themselves in terms of the role of human resources in the development of the performance of the Palestinian private schools according to the following variables (specialization, gender, years of experience, and age)? The study population consists of a sample of (100) principals of Palestinian private schools during the second semester of the academic year (2018/2019). The sample was randomly selected

Density functional theory (DFT) and molecular dynamic simulations (CPMD) studies on the Host-Guest cyclic molecular materials based on [Mo2O2S2]2+

Les polyoxométallates sont des clusters d’oxydes métalliques ayant de nombreuses applications physiques et chimiques dans les domaines de la catalyse, des matériaux, du magnétisme, de la médecine et de l’environnement. Les roues molybdates, développées à Versailles par l’équipe de F. Sécheresse sont construits à partir de synthons [Mo2O2S2]2+ dont la dimension, la forme, et la stabilité relative sont déterminées par l’inclusion de ligands di ou tri-carboxylates à chaîne saturée (Subérate C8 ; Pimelate C7, Adipate C6), insaturée ou aromatique (Oxalate, Terephtalate, Trimesate). Les cycles obtenus présentent une nucléarité variable qui peut être modulée par la présence de molécules organiques possédant deux fonctions carboxylates qui se greffent à l’intérieur de la roue inorganique. L’influence de ces molécules template sur la stabilité de l’ensemble Host-Guest et sur la déformation des anneaux polyoxothiomolybdates est étudiée au niveau DFT/BP86 avec des bases Slater triple-ζ de valence et de potentiels incluant les effets relativistes scalaires (ZORA). Les calculs reproduisent pour l’essentiel la séquence des stabilités observées et mettent en évidence le rôle des réseaux de liaisons hydrogène établis entre les groupements carboxylates et les molécules d’eau encapsulées dans le plan moyen de certains complexes. Les effets de solvant ont été pris en compte en utilisant un continuum diélectrique. Enfin, des simulations de dynamique Car-Parrinello (CPMD) effectuées sur les complexes [Mo12O12S12(OH)12Sat]2-, où Sat représente un dicarboxylate à chaîne saturée ont permis d’obtenir observé des changements de conformation affectant la chaîne carbonée flexible des dicarboxylates sans décomposition du complexe. Nous avons identifié d’autres minima locaux pour la Suberate, Pimelate, et Adipate.Polyoxometalates (POMs) are inorganic metal-oxygen anionic clutsers of nanometric size. They represent a wide family of molecules with versatile properties, which have been shown to be potentially attractive for catalysis, medicine, magnetism, or supramolecular chemistry. The dication [Mo2O2S2]2+ was used by the group of F. Sécheresse in order to form polyoxothiomolybdate rings whose size, shape, and relative stability are determined by the inclusion of saturated dicarboxylates (suberate C8 ; pimelate C7, adipate C6). The nuclearity of the ring seems monitored by the length of the alkyl chain. The influence of these template ligands on the stability of the whole host-guest complexes and the deformation of the ring have been studied at the DFT/BP86 level with Slater triple-ζ basis sets and pseudopotentials including relativistic effects. Our calculations are in agreement with the determined experimentally relative stabilities. The role of the water molecules connecting the carboxylate ends, and the stabilizing influence of the sets of hydrogen bonds have been emphasized. Solvation effects have been taken into account by means of the COSMO model. By using the Car-parrinello molecular dynamics scheme (CPMD), whe have observed such changes affecting the linear carboxylate assumed to be flexible at an average temperature of 500 K without the decomposition of the complex. Whe have located minima on the potential energy surface for the Suberate, Pimelate, Adipate

Density functional theory (DFT) and molecular dynamic simulations (CPMD) studies on the Host-Guest cyclic molecular materials based on [Mo2O2S2]2+

Les polyoxométallates sont des clusters d'oxydes métalliques ayant de nombreuses applications physiques et chimiques dans les domaines de la catalyse, des matériaux, du magnétisme, de la médecine et de l'environnement. Les roues molybdates, développées à Versailles par l'équipe de F. Sécheresse sont construites à partir de synthons [Mo2O2S2]2+ dont la dimension, la forme, et la stabilité relative sont déterminées par l'inclusion de ligands di ou tri-carboxylates à chaîne saturée (Subérate C8 ; Pimelate C7, Adipate C6), insaturée ou aromatique (Oxalate, Terephtalate, Trimesate). Les cycles obtenus présentent une nucléarité variable qui peut être modulée par la présence de molécules organiques possédant deux fonctions carboxylates qui se greffent à l'intérieur de la roue inorganique. L'influence de ces molécules template sur la stabilté de l'ensemble Host-Guest et sur la déformation des anneaux polyoxothiomolybdates est étudiée au niveau DFT/BP86 avec des bases Slater triple- de valence et des potentiels de coeur incluant les effets relativistes scalaires (ZORA). Les calculs reproduisent pour l'essentiel la séquence des stabilités observées et mettent en évidence le rôle des réseaux de liaisons hydrogène établis entre les groupements carboxylates et les molécules d'eau encapsulées dans le plan moyen de certains complexes. Les effets de solvant ont été pris en compte en utilisant un continuum diélectrique. Enfin, des simulations de dynamique Car-Parrinello (CPMD) effectuées sur les complexes [Mo12O12S12(OH)12Sat]2-, où Sat représente un dicarboxylate à chaîne saturée ont permis de modéliser les changements de conformation affectant la chaîne carbonée flexible des dicarboxylates sans décomposition du complexe. Ces simulations dynamiques ont permis de caractériser des minima locaux distincts des structures observées pour chacun des ligands flexiblesPolyoxometalates (POMs) are inorganic metal-oxygen anionic clutsers of nanometric size. They represent a wide family of molecules with versatile properties, which have been shown to be potentially attractive for catalysis, medicine, magnetism, or supramolecular chemistry. The dication [Mo2O2S2]2+ was used by the group of F. Sécheresse in order to form polyoxothiomolybdate rings whose size, shape, and relative stability are determined by the inclusion of saturated dicarboxylates (suberate C8 ; pimelate C7, adipate C6). The nuclearity of the ring appears to be monitored by the length of the alkyl chain. The influence of these template ligands on the stability of the whole hostguest complexes and the deformation of the ring have been studied at the DFT/BP86 level with Slater triple- basis sets and pseudopotentials including relativistic effects. Our calculations are in agreement with the experimentally determined relative stabilities. The role of the water molecules connecting the carboxylate ends, and the stabilizing influence of the networks of hydrogen bonds have been emphasized. Solvation effects have been taken into account by means of the COSMO model. By using the Car-Parrinello molecular dynamics (CPMD), we have observed such changes affecting the linear carboxylate assumed to be flexible at an average temperature of 500 K without the encountering any decomposition of the complex. Local energy minima corresponding to configurations of the encapsulated ligands suberate, pimelate and adipate distinct from the observed ones have been characterized from CPMD simulations

Role of Water on the Rotational Dynamics of the Organic Methylammonium Cation: A First Principles Analysis

Understanding the degradation mechanisms of lead-halide perovskites (CH3NH3PbI3) under exposure to liquid/aerosol water is an essential problem within the photovoltaic community. Herein we investigate both the static and the dynamic properties of the methylammonuim cation (MA) as it coordinates with invading water molecules (MA.(H2O)n, n = 1, 2, 3, 4) using both stationary state quantum mechanics and first principle molecular dynamics simulations. Various solvation structures of MA were characterized by their stabilization energies, dipoles, and Maximally-Localized Wannier Function (MLWF) centers. Calculation – and analysis – of vibrational shifts in the IR spectral region were performed for hydrated complexes; the locations of NH3+ stretching vibrations allude to significant hydrogen bonding between MA and the water molecules. Through Fourier analysis of the rotational dynamics on several MA · (H2O)n complexes, we conclude that the water molecules dampen the rotational motion of the MA as the intermolecular bonds formed between the water molecules and the MA act to hinder the rotation of the cation; these findings give explanatory support to earlier computational observations of humidity effects on perovskites (i.e., CH3NH3PbI3) materials. This work is a step toward understanding the water-MA cation interaction in bulk perovskites, thus providing greater understanding of in situ instability/degradation of perovskite bulk materials

Role of Water on the Rotational Dynamics of the Organic Methylammonium Cation: A First Principles Analysis

Understanding the degradation mechanisms of lead-halide perovskites (CH3NH3PbI3) under exposure to liquid/aerosol water is an essential problem within the photovoltaic community. Herein we investigate both the static and the dynamic properties of the methylammonuim cation (MA) as it coordinates with invading water molecules (MA.(H2O)n, n = 1, 2, 3, 4) using both stationary state quantum mechanics and first principle molecular dynamics simulations. Various solvation structures of MA were characterized by their stabilization energies, dipoles, and Maximally-Localized Wannier Function (MLWF) centers. Calculation – and analysis – of vibrational shifts in the IR spectral region were performed for hydrated complexes; the locations of NH+3 stretching vibrations allude to significant hydrogen bonding between MA and the water molecules. Through Fourier analysis of the rotational dynamics on several MA · (H2O)n complexes, we conclude that the water molecules dampen the rotational motion of the MA as the intermolecular bonds formed between the water molecules and the MA act to hinder the rotation of the cation; these findings give explanatory support to earlier computational observations of humidity effects on perovskites (i.e., CH3NH3PbI3) materials. This work is a step toward understanding the water-MA cation interaction in bulk perovskites, thus providing greater understanding of in situ instability/degradation of perovskite bulk materials

The Use of Clustering for GIS applications

Tato bakalářská práce se zabývá použitím metody shlukování v reálných GIS aplikacích. Cílem práce je vytvořit program využívající shlukovou knihovnu pro shlukování na základě různých atributů dat a nalézt vhodné nastavení shlukování dle GIS atributů. V úvodu práce je popsána problematika shlukování, za ní následuje popis řešení a diskuze experimentů.Katedra informatiky a výpočetní technikyObhájenoThis Bachelor thesis deals with using clustering methods in real GIS applications. The goal of this thesis is to create a program that uses the clustering library to cluster on the base of various data attributes and to find the right clustering settings from GIS attributes. In the beginning the problematics of clustering is described followed by the description of the solution and discussion of experiments

Etude par la théorie de la fonctionnelle de la densité et par la dynamique moléculaire Car-Parrinello des mécanismes de synthèse et d'isomérisation de nanomatériaux à base de polyoxométallates fonctionnalisés

Les polyoxométallates sont des clusters d oxydes métalliques ayant de nombreuses applications physiques et chimiques dans les domaines de la catalyse, des matériaux, du magnétisme, de la médecine et de l environnement. Les roues molybdates, développées à Versailles par l équipe de F. Sécheresse sont construites à partir de synthons [Mo2O2S2]2+ dont la dimension, la forme, et la stabilité relative sont déterminées par l inclusion de ligands di ou tri-carboxylates à chaîne saturée (Subérate C8 ; Pimelate C7, Adipate C6), insaturée ou aromatique (Oxalate, Terephtalate, Trimesate). Les cycles obtenus présentent une nucléarité variable qui peut être modulée par la présence de molécules organiques possédant deux fonctions carboxylates qui se greffent à l intérieur de la roue inorganique. L influence de ces molécules template sur la stabilté de l ensemble Host-Guest et sur la déformation des anneaux polyoxothiomolybdates est étudiée au niveau DFT/BP86 avec des bases Slater triple- de valence et des potentiels de coeur incluant les effets relativistes scalaires (ZORA). Les calculs reproduisent pour l essentiel la séquence des stabilités observées et mettent en évidence le rôle des réseaux de liaisons hydrogène établis entre les groupements carboxylates et les molécules d eau encapsulées dans le plan moyen de certains complexes. Les effets de solvant ont été pris en compte en utilisant un continuum diélectrique. Enfin, des simulations de dynamique Car-Parrinello (CPMD) effectuées sur les complexes [Mo12O12S12(OH)12Sat]2-, où Sat représente un dicarboxylate à chaîne saturée ont permis de modéliser les changements de conformation affectant la chaîne carbonée flexible des dicarboxylates sans décomposition du complexe. Ces simulations dynamiques ont permis de caractériser des minima locaux distincts des structures observées pour chacun des ligands flexiblesPolyoxometalates (POMs) are inorganic metal-oxygen anionic clutsers of nanometric size. They represent a wide family of molecules with versatile properties, which have been shown to be potentially attractive for catalysis, medicine, magnetism, or supramolecular chemistry. The dication [Mo2O2S2]2+ was used by the group of F. Sécheresse in order to form polyoxothiomolybdate rings whose size, shape, and relative stability are determined by the inclusion of saturated dicarboxylates (suberate C8 ; pimelate C7, adipate C6). The nuclearity of the ring appears to be monitored by the length of the alkyl chain. The influence of these template ligands on the stability of the whole hostguest complexes and the deformation of the ring have been studied at the DFT/BP86 level with Slater triple- basis sets and pseudopotentials including relativistic effects. Our calculations are in agreement with the experimentally determined relative stabilities. The role of the water molecules connecting the carboxylate ends, and the stabilizing influence of the networks of hydrogen bonds have been emphasized. Solvation effects have been taken into account by means of the COSMO model. By using the Car-Parrinello molecular dynamics (CPMD), we have observed such changes affecting the linear carboxylate assumed to be flexible at an average temperature of 500 K without the encountering any decomposition of the complex. Local energy minima corresponding to configurations of the encapsulated ligands suberate, pimelate and adipate distinct from the observed ones have been characterized from CPMD simulations.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF