Emergence of a potential charge-disproportionated insulating state in SrCrO3

We use a combination of density functional theory (DFT) and dynamical mean-field theory (DMFT) to investigate the potential emergence of a charge-disproportionated insulating phase in <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>SrCrO</a:mi><a:mn>3</a:mn></a:msub></a:math>, whereby the Cr cations disproportionate according to <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mn>3</b:mn><b:msup><b:mtext>Cr</b:mtext><b:mrow><b:mn>4</b:mn><b:mo>+</b:mo></b:mrow></b:msup><b:mo>→</b:mo><b:mn>2</b:mn><b:msup><b:mtext>Cr</b:mtext><b:mrow><b:mn>3</b:mn><b:mo>+</b:mo></b:mrow></b:msup><b:mo>+</b:mo><b:msup><b:mtext>Cr</b:mtext><b:mrow><b:mn>6</b:mn><b:mo>+</b:mo></b:mrow></b:msup></b:mrow></b:math> and arrange in ordered planes perpendicular to the cubic [111] direction. We show that the charge disproportionation couples to a structural distortion where the oxygen octahedra around the nominal <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:msup><c:mrow><c:mi>Cr</c:mi></c:mrow><c:mrow><c:mn>6</c:mn><c:mo>+</c:mo></c:mrow></c:msup></c:math> sites contract, while the octahedra surrounding the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:msup><d:mrow><d:mi>Cr</d:mi></d:mrow><d:mrow><d:mn>3</d:mn><d:mo>+</d:mo></d:mrow></d:msup></d:math> sites expand and distort. Our results indicate that the charge-disproportionated phase can be stabilized for realistic values of the Hubbard <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mi>U</e:mi></e:math> and Hund's <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mi>J</f:mi></f:math> parameters, but this requires a scaling of the DFT+DMFT double-counting correction by at least 35%. The disproportionated state can also be stabilized in <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mi>DFT</g:mi><g:mo>+</g:mo><g:mi mathvariant="script">U</g:mi></g:mrow></g:math> calculations for a specific magnetic configuration with antiparallel magnetic moments on adjacent <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:msup><i:mrow><i:mi>Cr</i:mi></i:mrow><i:mrow><i:mn>3</i:mn><i:mo>+</i:mo></i:mrow></i:msup></i:math> sites and no magnetic moment on the <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:msup><j:mrow><j:mi>Cr</j:mi></j:mrow><j:mrow><j:mn>6</j:mn><j:mo>+</j:mo></j:mrow></j:msup></j:math> sites. While this phase is higher in energy than other magnetic states that can arise in <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:msub><k:mi>SrCrO</k:mi><k:mn>3</k:mn></k:msub></k:math>, the presence of an energy minimum suggests that the charge-disproportionated state represents a metastable state of <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:msub><l:mi>SrCrO</l:mi><l:mn>3</l:mn></l:msub></l:math>. Published by the American Physical Society 2024