Ab initio crystal structure search and modeling of new High Entropy Ceramics
Title: Ab initio crystal structure search and modeling of new High Entropy Ceramics
SNIC Project: SNIC 2020/5-171
Project Type: SNIC Medium Compute
Principal Investigator: Farid Akhtar <farid.akhtar@ltu.se>
Affiliation: Luleå tekniska universitet
Duration: 2020-04-01 – 2021-04-01
Classification: 20501 10304 21001
Homepage: https://www.ltu.se/research/subjects/Materialteknik?l=en
Keywords:

Abstract

The applicant Farid Akhtar joined the Engineering Materials group at Luleå University of Technology (LTU) in March 2014, as part of the Division of Materials Science. His research focuses on the development of new materials with tailored properties for high temperature applications. Of special interest is the new class of high entropy alloys, called high entropy ceramics (HECs). This new class of materials are multiple component systems consisting of several ceramic compounds such metallic oxides, nitrides, borides or carbides. HECs show superior mechanical properties including high strength, high wear resistance, good corrosion and oxidation resistance over conventional alloys, especially at elevated temperatures. For this project studies of new HECs will be done by combining theoretical modeling and experiments. The experimental part carried out by PhD students Hanzhu Zhang and Sajid Alvi (Engineering Materials, LTU) and the theoretical modeling by Dr. Daniel Hedman (Applied Physics, LTU and AIST Japan). The theoretical part will focus on modeling HECs at the atomic level using Density Functional Theory (DFT). Crystal structures for new HECs will be predicted using different chemical compositions, 4 to 8 different metals together with boron, carbon or nitrogen using evolutionary crystal structure prediction (ECSP) together with DFT. ECSP can overcome large energy barriers and handle very large search spaces, making it ideal for complex multicomponent systems. In addition to running ECSP for finding new HEC the vast materialsproject.org database will be used together with DFT calculations to screen interesting HEC chemical compositions. To calculate reliable properties for HECs (lattice parameters, formation enthalpies, electrical, mechanical and thermal properties, etc.) using DFT, the ECSP predicted HECs will be modeled using Special Quasirandom Structures (SQS). By combining theoretical modelling and experiments we aim to increase the understanding of HECs, their properties, formation, characterization and to predict new novel HECs. This is a continuation of our project SNIC 2019/3-129 which has led to one publication [Zhang et al. A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite, Dalton Trans. 2019] which was included in the licentiate thesis of Hanzhu Zhang [Synthesis of metallic/high entropy ceramic composite and a study of the phase transformation mechanism, LTU, 2019]. The work is progressing with one manuscript already submitted and under review and one manuscript soon to be submitted.