{"title":"Hydrogen Bonding in Parascorodite and Relative Stability of Fe(AsO4)⋅2H2O Polymorphs","authors":"S. V. Krivovichev","doi":"10.1134/s1075701523070061","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Density functional theory (DFT) has been used with CRYSTAL14 program to optimize hydrogen atom positions in the crystal structure of parascorodite Fe(AsO<sub>4</sub>)⋅2H<sub>2</sub>O. It has been shown that taking into account hydrogen bonding, the structure forms six-membered asymmetrical cycles –Fe1–O1–H1<sup>…</sup>O3–As–O2– and eight-membered cycles –Fe1–O1–H2<sup>…</sup>O2–Fe1–O2<sup>…</sup>H2–O1– with lateral topological symmetry. Calculation of the structural complexity parameters for scorodite and parascorodite and their comparison with thermodynamic characteristics shows that the Fe(AsO<sub>4</sub>)⋅2H<sub>2</sub>O polymorph modifications correspond well to Goldsmith’s rule that states that metastable transitional polymorphs are structurally simpler than thermodynamically stable phases. Scorodite is a stable phase, whereas parascorodite is metastable, which agrees well with the conclusions made in the previous works. Crystallization of parascorodite under natural conditions of oxidation zones of ore-mineral deposits may occur due to the high speed of its nucleation as a metastable phase, i.e., due to the kinetic stabilization of its structure.</p>","PeriodicalId":12719,"journal":{"name":"Geology of Ore Deposits","volume":"17 1","pages":""},"PeriodicalIF":0.8000,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geology of Ore Deposits","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1134/s1075701523070061","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Density functional theory (DFT) has been used with CRYSTAL14 program to optimize hydrogen atom positions in the crystal structure of parascorodite Fe(AsO4)⋅2H2O. It has been shown that taking into account hydrogen bonding, the structure forms six-membered asymmetrical cycles –Fe1–O1–H1…O3–As–O2– and eight-membered cycles –Fe1–O1–H2…O2–Fe1–O2…H2–O1– with lateral topological symmetry. Calculation of the structural complexity parameters for scorodite and parascorodite and their comparison with thermodynamic characteristics shows that the Fe(AsO4)⋅2H2O polymorph modifications correspond well to Goldsmith’s rule that states that metastable transitional polymorphs are structurally simpler than thermodynamically stable phases. Scorodite is a stable phase, whereas parascorodite is metastable, which agrees well with the conclusions made in the previous works. Crystallization of parascorodite under natural conditions of oxidation zones of ore-mineral deposits may occur due to the high speed of its nucleation as a metastable phase, i.e., due to the kinetic stabilization of its structure.
期刊介绍：
Geology of Ore Deposits is a periodical covering the topic of metallic and nonmetallic mineral deposits, their formation conditions, and spatial and temporal distribution. The journal publishes original scientific articles and reviews on a wide range of problems in theoretical and applied geology. The journal focuses on the following problems: deep geological structure and geodynamic environment of ore formation; distribution pattern of metallogenic zones and mineral deposits; geology and formation environment of large and unique metallic and nonmetallic deposits; mineralogy of metallic and nonmetallic deposits; physicochemical and isotopic characteristics and geochemical environment of ore deposition; evolution of ore-forming systems; radiogeology and radioecology, economic problems in exploring, developing, and mining of ore commodities.
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