Role of local structure in the optical and electronic properties of oxygen vacancies in different crystal phases of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Ga</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub

We investigate the structural, electronic, and optical properties of oxygen vacancies (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi mathvariant="normal">V</a:mi><a:mi mathvariant="normal">O</a:mi></a:msub></a:math>) in crystalline <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mi>α</d:mi><d:mo>,</d:mo><d:mo> </d:mo><d:mi>β</d:mi></d:math>, and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mi>ε</e:mi><e:mtext>−</e:mtext><e:msub><e:mi>Ga</e:mi><e:mn>2</e:mn></e:msub><e:msub><e:mi mathvariant="normal">O</e:mi><e:mn>3</e:mn></e:msub></e:mrow></e:math> using density functional theory (DFT) calculations with the PBE0-TC-LRC functional. Our results reveal that the charge transition levels (CTLs) associated with <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:msub><g:mi mathvariant="normal">V</g:mi><g:mi mathvariant="normal">O</g:mi></g:msub></g:math> exhibit significant variations depending on the crystal phase and the coordination environment of surrounding atoms. In particular, <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mrow><j:msub><j:mi mathvariant="normal">V</j:mi><j:mi mathvariant="normal">O</j:mi></j:msub><j:mi mathvariant="normal">s</j:mi></j:mrow></j:math> surrounded by tetrahedral Ga atoms (<n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mrow><n:mi>T</n:mi><n:mtext>-Ga</n:mtext></n:mrow></n:math>) exhibit deeper CTLs compared to those surrounded by octahedral Ga atoms (<o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:mrow><o:mi>O</o:mi><o:mtext>-Ga</o:mtext></o:mrow></o:math>). We also observe distinct atomic relaxations, with larger displacements of <p:math xmlns:p="http://www.w3.org/1998/Math/MathML"><p:mrow><p:mi>T</p:mi><p:mtext>-Ga</p:mtext></p:mrow></p:math> atoms compared to <q:math xmlns:q="http://www.w3.org/1998/Math/MathML"><q:mrow><q:mi>O</q:mi><q:mtext>-Ga</q:mtext></q:mrow></q:math> atoms in the vicinity of <r:math xmlns:r="http://www.w3.org/1998/Math/MathML"><r:mrow><r:msub><r:mi mathvariant="normal">V</r:mi><r:mi mathvariant="normal">O</r:mi></r:msub><r:mi mathvariant="normal">s</r:mi></r:mrow></r:math>. Using linear-response time-dependent DFT, we investigate the optical transitions of <v:math xmlns:v="http://www.w3.org/1998/Math/MathML"><v:msub><v:mi mathvariant="normal">V</v:mi><v:mi mathvariant="normal">O</v:mi></v:msub></v:math> and identify two distinct types of transitions: defect state to conduction band state and valence band to defect state. These results can be used to better understand the optical properties of <y:math xmlns:y="http://www.w3.org/1998/Math/MathML"><y:msub><y:mi mathvariant="normal">V</y:mi><y:mi mathvariant="normal">O</y:mi></y:msub></y:math> defects in <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML"><bb:mrow><bb:msub><bb:mi>Ga</bb:mi><bb:mn>2</bb:mn></bb:msub><bb:msub><bb:mi mathvariant="normal">O</bb:mi><bb:mn>3</bb:mn></bb:msub></bb:mrow></bb:math> films. Published by the American Physical Society 2024