Modeling and Simulation of Advanced Ceramic Materials

Innovative materials used in high-technology applications are called advanced materials. These materials can be completely new or typical traditional materials (e.g., metals, ceramics)whose properties have been enhanced to become advanced. This talk will cover the theoretical investigation of various advanced ceramic materials in connection to the experimental results. The first part will include the basics of modeling and structure prediction of ceramic materials, such as global optimization, quantum mechanics, and supercell method, as well as current developments in the Inorganic Crystal Structure Database (ICSD), theoretical crystal structure data, and data mining.In the next part, theoretical methods will be applied to the specific ceramic compounds. A plethora of state-of-the-art quantum mechanical methods will be presented, including Density-functional theory (DFT),LDA-PZ and GGA-PBE, or hybrid B3LYP and HSE functionals, and a combination of quantum mechanics with data mining and global optimization, as well as the newly developed Primitive Cell approach for Atom Exchange (PCAE) method applied on ZnO/ZnS polytypic (hetero)structures and unknown Cr2SiN4 compounds. Finally, the theoretical modeling of materials properties has been presented. Since many of the investigated materials show a large number of desirable properties for industrial applications,ab initio calculations of electronic, elastic, and mechanical properties will be presented and compared with experiments when available.XI Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 18-20, 2023; Belgrad

BiFeO3 perovskites: theoretical and experimental investigations

Bismuth ferrite (BiFeO3) is one of the most studied multiferroic system. BiFeO3 has been synthesized by controlled hydrothermal process, where the particles of small sizes and with high purity were obtained. Structural analysis showed that nonannealed powder can be perfectly fitted to rhombohedral space group R3c as αBiFeO3 phase. In addition, a structure prediction has been performed and 11 additional BiFeO3 modifications have been proposed. In the next phase, an ab initio optimization of predicted structures has been performed and the structure of the γphase has been elucidated. In addition, electronic and magnetic properties of BiFeO3 were investigated using combination of experimental and theoretical methods. Theoretical studies were performed using a full potential linearized augmented plane-waves plus local orbital (FP(L)APW+lo) method, based on density functional theory (DFT). HRTEM analysis confirmed existence of twin stacking faults, which are responsible for enhanced magnetic properties. EPR measurements suggested existence of electrons trapped by vacancies or defects, while magnetic behavior of synthesized material was investigated by SQUID

Hafnium Carbide: Prediction of Crystalline Structures and Investigation of Mechanical Properties

Hafnium carbide (HfC) is a refractory compound known for its exceptional mechanical, thermal, and electrical properties. This compound has gained significant attention in materials science and engineering due to its high melting point, extreme hardness, and excellent thermal stability. This study presents crystal structure prediction via energy landscape explorations of pristine hafnium carbide supplemented by data mining. Apart from the well-known equilibrium rock salt phase, we predict eight new polymorphs of HfC. The predicted HfC phases appear in the energy landscape with known structure types such as the WC type, NiAs type, 5-5 type, sphalerite (ZnS) type, TlI type, and CsCl type; in addition, we predict two new structure types denoted as ortho_HfC and HfC_polytype, respectively. Moreover, we have investigated the structural characteristics and mechanical properties of hafnium carbide at the DFT level of computation, which opens diverse applications in various technological domains

Zinc oxide: Connecting theory and experiment

Zinc oxide (ZnO) is a material with a great variety of industrial applications including high heat capacity, thermal conductivity and temperature stability. Clearly, it would be of great importance to find new stable and/or metastable modifications of zinc oxide, and investigate the influence of pressure and/or temperature on these structures, and try to connect theoretical results to experimental observations. In order to reach this goal, we performed several research studies, using modern theoretical methods. We have predicted possible crystal structures for ZnO using simulated annealing (SA), followed by investigations of the barrier structure using the threshold algorithm (TA). Finally, we have performed calculations using the prescribed path algorithm (PP), where connections between experimental structures on the energy landscape, and in particular transition states, were investigated in detail. The results were in good agreement with previous theoretical and experimental observations, where available, and we have found several additional (meta)stable modifications at standard, elevated and negative pressures. Furthermore, we were able to gain new insight into synthesis conditions for the various ZnO modifications and to connect our results to the actual synthesis and transformation routes

Structural properties of full-scope AlN/BN compounds investigated using ab initio calculations

In the last few decades, aluminum nitride (AlN) and boron nitride (BN) have become a point of interest to many researchers and scholars from different disciplines around the world. Due to its attractive properties, AlN has been successfully used in various applications, starting from advanced ceramics materials, additive for grain size control in micro-alloyed steels, through optoelectronics and microelectronics, and finally to semiconductors. On the other hand, BN has broad applications in various fields, such as 2D material, lubricant material, superhard and semiconductor material as well as many others. This study focuses on the mixed AlN/BN compounds, in particular, boron-rich AlN and aluminum-rich BN systems, thus having the entire range of AlN/BN compositions. The special focus was on structural properties investigated using the hybrid B3LYP method. Important structural properties were investigated to offer novel technological and industrial applications of mixed AlN/BN materials.International Conference on Structural Integrity 2023 (ICSI 2023

Theoretical investigations of novel zinc oxide polytypes and in-depth study of their electronic properties

Zinc oxide is one of the most investigated compounds in materials science, both experimentally and theoretically, while in nature it appears only rarely, as the mineral zincite. Yet there are still many open questions: Is it still possible to observe or synthesize new modifications of zinc oxide? And can we improve the properties of a material that has already been investigated in thousands of studies? What is the connection between zincite, zinc sulfide and zinc oxide, and can we finally explain the controversial mineral matraite? In short, Yes: the answer to these questions is polytypism. We identify a multitude of possible stable polytypes for zinc oxide, and we show that by varying the stacking order, we can fine-tune the electronic properties such as the direct primary and secondary band gaps in zinc oxide without adding dopant atoms

DFT study of the Cr2SiN4 under extreme pressure conditions

Recently predicted Cr2SiN4 phases have been further investigated using ab initio methods to explore their behavior under extreme conditions of pressure. Thermodynamic functions for several different modifications have been calculated for the pressure range from 0 to 10 GPa using the GGAPBE functional. Detailed analysis of the mechanical properties under pressure has been performed using the CRYSTAL solid-state quantum-chemical program. The change in volume, energy, and bulk modulus with pressure elevation has been discussed for each of the phases investigated within this study. The highest value of bulk modulus is found in the equilibrium spinel type modification showing the highest capacity of resistance to volume change under pressure. As this material could potentially have a very wide industrial and technological application, these findings could be of great importance as they provide more insight into this novel Cr2SiN4 compound, and especially its behaviour in the extreme environment

Theoretical study of ground state properties of Na+ , Cs+ , Mg2+ AND Ba2+ doped mayenite and its electride forms under extreme conditions

Calculations of band structure and electronic density distribution near Fermi energy have been performed for complex nanoporous oxide mayenite 12CaO·7Al2O3 (C12A7) on the ab initio level. The electronic structure of mayenite doped with selected cations from the 1st and 2nd group of the periodic table of elements (Na+ , Cs+ , Mg2+ , and Ba2+) have also been calculated in order to estimate the effect of cationic doping on structural, electronic, and optical properties of mayenite. Partial and complete substitution of the interstitial oxygen anions (there are two O2- anions per unit cell) with electrons (e- “doping”) is also considered in ab initio calculations to observe differences in electronic structure (such as band gap and Fermi level) during the transition from insulator (regular mayenite crystal with O 2- anions in interstitial places) to electride

Crystal Structure and Properties of Theoretically Predicted AlB12

Aluminum borides have various industrial applications, used in fuels, explosives, abrasives, and as additives to consolidated materials based on boron carbide. The structure of AlB12 is similar to that of boron carbide, including almost regular icosahedrons of boron atoms. The absence of the structure data of some higher aluminum borides and the presence of a large number of reflexes in their diffraction patterns makes the identification of phase compositions very difficult and limits the possibilities of the computer modeling of the AlB12. The crystal structure of AlB12 is usually considered as tetragonal α-AlB12 (space group P43212) and orthorhombic γ-AlB12 (space group P212121) which can be synthesized from high-temperature Al-B melts. In our work, we have performed ab initio optimization of the experimentally observed Yannoni’s AlB12 using GGA-PBE functional and obtained relaxed unit cell parameters and atomic positions. Furthermore, we have predicted three different AlB12 structure candidates obtained as a result of the ICSD data mining. The most favorable structure according to total energy ranking was found in the UB12 structure type, which crystallizes in the cubic space group Fm-3m. Therefore, for the new cubic AlB12, we have calculated mechanical properties on different pressures and made the comparison with available experimental data in the AlB12 system