Threshold Displacement Energies in Lead Halide Perovskites from <i>Ab Initio</i> Molecular Dynamics Simulations
Raúl Duque, Ahmad R. Kirmani, Ian R. Sellers, Mario F. Borunda
Abstract
Predicting radiation damage to materials requires estimating the threshold displacement energy ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <a:msub> <a:mi>E</a:mi> <a:mi>d</a:mi> </a:msub> </a:math> ). We calculate <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <d:msub> <d:mi>E</d:mi> <d:mi>d</d:mi> </d:msub> </d:math> using molecular dynamics for the lead halide perovskites MA <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <g:mrow> <g:mi>Pb</g:mi> <g:mi mathvariant="normal">I</g:mi> </g:mrow> </g:math> <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <k:msub> <k:mi/> <k:mn>3</k:mn> </k:msub> </k:math> , FA <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <n:mrow> <n:mi>Pb</n:mi> <n:mi mathvariant="normal">I</n:mi> </n:mrow> </n:math> <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <r:msub> <r:mi/> <r:mn>3</r:mn> </r:msub> </r:math> , and <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <u:mrow> <u:mi>Cs</u:mi> <u:mi>Pb</u:mi> <u:mi mathvariant="normal">I</u:mi> </u:mrow> </u:math> <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <y:msub> <y:mi/> <y:mn>3</y:mn> </y:msub> </y:math> . The <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <bb:msub> <bb:mi>E</bb:mi> <bb:mi>d</bb:mi> </bb:msub> </bb:math> values that we obtain, which are considerably lower than those commonly assumed in the literature for several species, hold significant implications for predicting radiation damage to materials. We perform Monte Carlo simulations with the molecular dynamics (AIMD) obtained <eb:math xmlns:eb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <eb:msub> <eb:mi>E</eb:mi> <eb:mi>d</eb:mi> </eb:msub> </eb:math> and compare them to simulations using the default <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <hb:msub> <hb:mi>E</hb:mi> <hb:mi>d</hb:mi> </hb:msub> </hb:math> . Our results show an increase in specific vacancies in halide perovskites that is not captured in simulations using the default <kb:math xmlns:kb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <kb:msub> <kb:mi>E</kb:mi> <kb:mi>d</kb:mi> </kb:msub> </kb:math> values. This suggests that the default <nb:math xmlns:nb="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <nb:msub> <nb:mi>E</nb:mi> <nb:mi>d</nb:mi> </nb:msub> </nb:math> values may not accurately predict the radiation damage in these materials, potentially leading to underestimation of the damage. These results are discussed in the context of the radiation hardness of the materials and suggest that they get damaged when exposed to radiation, but they are resilient due to processes.