PENGARUH BIAXIAL DAN UNIAXIAL STRAIN PADA STRUKTUR ELEKTRONIK TiO2 ANATASE: KAJIAN KOMPUTASI MENGGUNAKAN DENSITY FUNCTIONAL THEORY

Farahdina Zain, NIM.: 19106020045 (2023) PENGARUH BIAXIAL DAN UNIAXIAL STRAIN PADA STRUKTUR ELEKTRONIK TiO2 ANATASE: KAJIAN KOMPUTASI MENGGUNAKAN DENSITY FUNCTIONAL THEORY. Skripsi thesis, UIN SUNAN KALIJAGA YOGYAKARTA.

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Abstract

A computational study has been done on the effect of biaxial and uniaxial strains on the geometric structure and electronic structure of anatase TiO2. This study aims to perform geometry optimization, optimized crystal structure modeling, and calculation of the electronic structure of anatase TiO2 with biaxial and uniaxial strain variations. The method used in this study is Density Functional Theory with an exchange-correlation generalized gradient approximation (GGA) function based on Perdew-Burke Ernzerhof (PBE) and Ultrasoft pseudopotential types. The research stages consisted of constructing a 12-atom unit cell, optimizing lattice constants with BM-EOS fittings, and administering biaxial and uniaxial strains with variations of 4%, -4%, 8%, -8%, 12, -12%, 16% and -16%, as well as the calculation of the electronic structure for each strain variation. The results obtained from this study indicate that changes occur in the crystal structure and electronic structure of anatase TiO2 due to strain. Applying strain to the anatase TiO2 crystal structure shows that when the crystal lattice is strained, the atoms in the lattice will move to overcome the deformation. If the strain exceeds the material's ability to cope with the deformation, the bonds between atoms can break and lead to the formation of crystal defects. The results of giving a 16% biaxial tensile strain to the anatase TiO2 unit cell show broken bonds and can disrupt the stability of the material geometry. Biaxial and uniaxial strains are proven to change the band gap energy value when compared to a pure system with a band gap energy of 1.704 eV. Biaxial compressive strain (-4%, -12%, -16%) tends to increase band gap energy, and biaxial tensile strain (4%, 12%, 16%) reduces band gap energy. Whereas in uniaxial strains, the tendency is reversed. This study's band structure of all anatase TiO2 unit cell systems show indirect band gap characteristics.

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