ASM 2019

Poster (P2)


Exploring the thermodynamic stability of N-, Mn-doped and Mn-N co-doped SrTiO3 perovskite: A hybrid density functional study

Manish Kumar* and Saswata Bhattacharya

 

Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016

 

*manish.kumar[at]physics.iitd.ac.in

 

SrTiO3 perovskite, considered as a promising photocatalyst due to its electronic structure and high chemical stability. Metal and non-metal dopants have been widely investigated in order to enhance the visible light absorption and improve the photocatalytic activity. Density Functional Theory (DFT) calculations show that the metal (viz. manganese and rhodium) and non-metal (viz. nitrogen) dopants have significant role in reducing the band gap and thereby making the material to be useful for photocatalysis. We address the role of metal, non-metal and co-dopant impurity in bulk SrTiO3 perovskite using first-principles based calculation under the framework of DFT. We have found that hybrid functional is essential to address the system, while DFT with local/semi-local functionals are insufficient even for a qualitative analysis. The co-doping of metal and non-metal (viz. (Mn)Ti(N)O) reduces the band gap with respect to SrTiO3 pristine by shifting the band edges. This ameliorates the photocatalytic properties of the material. We also address a detailed study for different configurations possible for the impurities including: substitutional (XO/Ti/Sr), interstitial (XO)O/Ti/Sr and (X2)O/Ti/Sr in which interstitial X shares a lattice site with XO/Ti/Sr. Our result reveals that in case of N-related defects, NO is energetically favorable over other N impurity configurations in SrTiO3. NO helps in reducing the band gap, but introduces the localized occupied and unoccupied states in the visible region, which degrade the photocatalytic activity. However, in case of co-doping of Mn and N, Mn helps in passivating those unoccupied states. We have also found that the band edge positions could be controlled using co-doping of Mn and N in order to promote redox reaction for photocatalysis. Also, the absorption spectra of MnTiNO is found to lie in the visible region due to reduction in band gap to 1.94 eV.

 

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