AB INITIO STUDY ON ELECTRONIC STRUCTURE, OPTICAL AND TRANSPORT PROPERTIES OF X2OBA4 (X = SB, BI) ANTI RUDDLESDEN-POPPER COMPOUND WITH FP-LAPW METHOD

• Main Author: Gde Wira Wisnanta Dharma, I
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/83520
• Institution: Institut Teknologi Bandung

Layered materials has been thoroughly studied for optoelectronic, ferroelectric, spintronic, and thermoelectric materials. One of the newly found structure of such family is anti Ruddlesden-Popper structure which consists of anti-perovskite and rocksalt-like layer. These research focus on ab initio study of X2OBa4 (X = Sb. Bi) anti Ruddlesden-Popper series with FP-LAPW method. There is one possible structure for Sb2OBa4 and three possible structures for Bi2OBa4 with different O configurations. These research aim to the study electronic structure, optical properties, transport properties, and its correlation to O position shift. Optical properties are calculated with independent particle approximation using Kubo Greenwood equation. Transport properties are calculated with constant relaxation time approximation using semiclassical Boltzmann transport equation. Electronic structure calculation show medium-gap semiconductor and Eg values within 0,59 – 1,15 eV range. Position shift affects Eg by changing orbital overlap of O. Optical and transport properties are then calculated with modified Becke-Johnson potential to describe electronic structure more accurately. Optical properties calculation shows static dielectric constants within 7,0 – 9,5 range and strong absorption within 5×105 – 1,2×106 cm-1 in UV region. Position shift creates additional polarization and change the value of static dielectric constants in the z-direction. Transport properties calculation shows high electronic figure-of-merit (ZTel ? 40) at low temperature (T < 600 K) for dopant concentration within 1017 – 5×1018 cm-3. Position shift creates flat bands in valence and conduction band which increases Seebeck coefficient (S > 750 ?V/K). Accounting for minimum lattice thermal conductivity, theoretical figure-of-merit decreased within 0,37 – 1,18 with its maximum at medium temperature (650 – 850 K). These properties demonstrate potensial application as UV absorbent material and low temperature thermoelectric material by thermal conductivity optimization.