The rule of four: anomalous stoichiometries of inorganic compounds

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This paper reports the anomalous abundance of inorganic compounds with primitive unit cells containing a multiple of four atoms, termed the "rule of four," which is linked to low symmetry and loosely packed structures.

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This paper studies an observed pattern in inorganic crystal compositions: compounds whose primitive unit cell contains an atom count that is a multiple of four are anomalously abundant, a phenomenon the authors term the “rule of four.” Using experimentally known compounds plus analyses relating this abundance to crystal-structure descriptors (from symmetries and energies to global packing and local atomic-position similarity), the authors find that the overabundance does not align with low-energy or high-symmetry structures; instead, rule-of-four structures show low symmetry and loosely packed arrangements that maximize free volume, and the authors relate the effect to local structural symmetries using a hybrid supervised-unsupervised machine learning approach. A major limitation explicitly noted in the abstract is that this rule is not previously reported or studied, implying a nascent finding that requires further validation beyond descriptive correlation. The paper does not explicitly discuss endometriosis or adenomyosis; it was included in the corpus via a keyword match in the upstream search index.

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Abstract

Abstract Why are materials with specific characteristics more abundant than others? This is a fundamental question in materials science and one that is traditionally difficult to tackle, given the vastness of compositional and configurational space. We highlight here the anomalous abundance of inorganic compounds whose primitive unit cell contains a number of atoms that is a multiple of four. This occurrence - named here the rule of four - has to our knowledge not previously been reported or studied. Here, we first highlight the rule's existence, especially notable when restricting oneself to experimentally known compounds, and explore its possible relationship with established descriptors of crystal structures, from symmetries to energies. We then investigate this relative abundance by looking at structural descriptors, both of global (packing configurations) and local (the smooth overlap of atomic positions) nature. Contrary to intuition, the overabundance does not correlate with low-energy or high-symmetry structures; in fact, structures which obey the rule of four are characterized by low symmetries and loosely packed arrangements maximizing the free volume. We are able to correlate this abundance with local structural symmetries, and visualize the results using a hybrid supervised-unsupervised machine learning method.
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The rule of four: anomalous stoichiometries of inorganic compounds | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The rule of four: anomalous stoichiometries of inorganic compounds Elena Gazzarrini, Rose Cersonsky, Marnik Bercx, Simon Adorf, Nicola Marzari This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3206854/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 12 Apr, 2024 Read the published version in npj Computational Materials → Version 1 posted 11 You are reading this latest preprint version Abstract Why are materials with specific characteristics more abundant than others? This is a fundamental question in materials science and one that is traditionally difficult to tackle, given the vastness of compositional and configurational space. We highlight here the anomalous abundance of inorganic compounds whose primitive unit cell contains a number of atoms that is a multiple of four. This occurrence - named here the rule of four - has to our knowledge not previously been reported or studied. Here, we first highlight the rule's existence, especially notable when restricting oneself to experimentally known compounds, and explore its possible relationship with established descriptors of crystal structures, from symmetries to energies. We then investigate this relative abundance by looking at structural descriptors, both of global (packing configurations) and local (the smooth overlap of atomic positions) nature. Contrary to intuition, the overabundance does not correlate with low-energy or high-symmetry structures; in fact, structures which obey the rule of four are characterized by low symmetries and loosely packed arrangements maximizing the free volume. We are able to correlate this abundance with local structural symmetries, and visualize the results using a hybrid supervised-unsupervised machine learning method. Physical sciences/Physics/Condensed-matter physics Physical sciences/Materials science/Condensed-matter physics Full Text Additional Declarations (Not answered) Supplementary Files TheruleoffourSI.pdf Cite Share Download PDF Status: Published Journal Publication published 12 Apr, 2024 Read the published version in npj Computational Materials → Version 1 posted Editorial decision: revise 20 Sep, 2023 Review # 1 received at journal 07 Sep, 2023 Review # 3 received at journal 05 Sep, 2023 Reviewer # 3 agreed at journal 05 Sep, 2023 Review # 2 received at journal 05 Sep, 2023 Reviewer # 2 agreed at journal 05 Sep, 2023 Reviewer # 1 agreed at journal 15 Aug, 2023 Reviewers invited by journal 14 Aug, 2023 Submission checks completed at journal 27 Jul, 2023 First submitted to journal 26 Jul, 2023 Editor assigned by journal 26 Jul, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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