Sodium chloride induced nitrogen salt with cyclo- N5 anions at high pressure

The energy landscape of sodium chloride-nitrogen mixtures has been comprehensively explored to examine the ability of the formation of unknown compounds under pressures of up to 100 GPa, using swarm-intelligence structure prediction methodology and first-principles calculations. We identified a thermodynamically stable <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>NaN</a:mi><a:mn>5</a:mn></a:msub><a:msub><a:mi>ClN</a:mi><a:mn>5</a:mn></a:msub></a:mrow></a:math> compound containing two cyclo-<b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msub><b:mi mathvariant="normal">N</b:mi><b:mn>5</b:mn></b:msub></b:math> species under pressures exceeding 53 GPa, representing milder conditions in comparison to those requisite for pure solid nitrogen. In <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msub><d:mi>NaN</d:mi><d:mn>5</d:mn></d:msub><d:msub><d:mi>ClN</d:mi><d:mn>5</d:mn></d:msub></d:mrow></d:math>, the high electron affinity of the cyclo-<e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:msub><e:mi mathvariant="normal">N</e:mi><e:mn>5</e:mn></e:msub></e:math> motif allows it to oxidize the chlorine atoms, resulting in the formation of two cyclo-<g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:msub><g:mi mathvariant="normal">N</g:mi><g:mn>5</g:mn></g:msub></g:math> anions. Additionally, the weak covalent interactions between Cl and nearby N atoms plays a key role in stabilization of structure. It has been demonstrated that simple <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:msub><i:mi>NaN</i:mi><i:mn>5</i:mn></i:msub></i:math> salt was a suitable precursor for the synthesis of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mrow><j:msub><j:mi>NaN</j:mi><j:mn>5</j:mn></j:msub><j:msub><j:mi>ClN</j:mi><j:mn>5</j:mn></j:msub></j:mrow></j:math> at high pressure. molecular dynamics simulations demonstrated the recoverability of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mrow><k:msub><k:mi>NaN</k:mi><k:mn>5</k:mn></k:msub><k:msub><k:mi>ClN</k:mi><k:mn>5</k:mn></k:msub></k:mrow></k:math> as a metastable phase at ambient pressure-temperature conditions. Additionally, <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mrow><l:msub><l:mi>NaN</l:mi><l:mn>5</l:mn></l:msub><l:msub><l:mi>ClN</l:mi><l:mn>5</l:mn></l:msub></l:mrow></l:math> exhibits a higher energy density of 3.86 kJ/g and a lower mass density of 1.67 g/<m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:msup><m:mrow><m:mi>cm</m:mi></m:mrow><m:mn>3</m:mn></m:msup></m:math> in comparison to metal pentazolate salts, highlighting its potential as a high energy-density material.