Advancing Vapor-Liquid Equilibrium Predictions with the OPPES United Atom Forcefield for Associating Fluids

Advancing Vapor-Liquid Equilibrium Predictions with the OPPES United Atom Forcefield for Associating Fluids | 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 Research Article Advancing Vapor-Liquid Equilibrium Predictions with the OPPES United Atom Forcefield for Associating Fluids Sunghyun Jang, Dongjin Kim, Yongjin Lee This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7053206/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 07 Oct, 2025 Read the published version in Korean Journal of Chemical Engineering → Version 1 posted 4 You are reading this latest preprint version Abstract In this study, we extend the OPPES united atom force field to normal alcohols, glycols, and alkoxyethanols by optimizing new potential parameters based on the previously developed OPPES n-alkane and ether models. Bonded interaction parameters were primarily adopted from the TraPPE-UA model, except for equilibrium bond lengths and bending angles, which were obtained through density functional theory (DFT) geometry optimizations. Partial charges for ether oxygens and neighboring carbon pseudo-atoms were taken from the OPPES ether model, while those for hydroxyl oxygens and hydrogens were adopted from the AMBER model. The alpha carbon's charge was determined by enforcing charge neutrality. Lennard-Jones (LJ) parameters for hydroxyl oxygen and hydrogen were fitted to experimental liquid densities and vapor pressures of representative n-alcohols. Using the optimized parameters, we performed configurational-bias Monte Carlo simulations in the NVT ensemble for five n-alcohols (methanol to 1-octanol), two glycols (1,2-ethanediol and 1,3-propanediol), and three alkoxyethanols (2-methoxyethanol to 2-propoxyethanol). Additionally, NPT Gibbs ensemble Monte Carlo simulations were conducted for a binary n-heptane + 2-propoxyethanol system to evaluate phase behavior and local composition enhancements. Hydrogen bonding statistics were analyzed to assess the model’s performance in capturing associative interactions and fluid structure. Overall, the OPPES model yielded improved predictions of thermophysical properties compared to the TraPPE-UA model, especially near critical conditions, demonstrating its potential as a reliable and transferable force field for associating fluids. united atom force field Gibbs ensemble Monte Carlo simulation associating fluids hydrogen bonding vapor-liquid phase equilibria Full Text Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Published Journal Publication published 07 Oct, 2025 Read the published version in Korean Journal of Chemical Engineering → Version 1 posted Reviewers agreed at journal 14 Jul, 2025 Reviewers invited by journal 14 Jul, 2025 Editor assigned by journal 09 Jul, 2025 First submitted to journal 05 Jul, 2025 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. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7053206","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":485309005,"identity":"bf6a43b7-ebd9-4804-ac70-bda7e66181da","order_by":0,"name":"Sunghyun Jang","email":"","orcid":"","institution":"Kemira Water Solutions","correspondingAuthor":false,"prefix":"","firstName":"Sunghyun","middleName":"","lastName":"Jang","suffix":""},{"id":485309006,"identity":"e9527ebb-9eac-4b82-bc12-809560c65dfb","order_by":1,"name":"Dongjin Kim","email":"","orcid":"","institution":"Inha University","correspondingAuthor":false,"prefix":"","firstName":"Dongjin","middleName":"","lastName":"Kim","suffix":""},{"id":485309007,"identity":"0085b0f1-a678-4bd5-bf2e-d80fb607ebdc","order_by":2,"name":"Yongjin Lee","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA90lEQVRIie3RMWvCQBjG8ScIl+Uw60mh6Ue4Eggu4lcxCJkyODoeFDJZurbfwrFDh8hBsgTnDA7JEhwEFUEodOhbBcczY4f7jy/3417uAJvtvyYk0AeceoLsMnBUF8KAnuxO/iLCBLoQWbzq7XC2AXNf8nnzufHh6tr5+DKQch0PhWzBeB5XUdk+Kx5LZ9kaSJWEUkhNWyVhFaWadkroIbIuxN+fZ0TGytvdJUF9vYUzEImUoFuWBjIoy5AeWXPG40AQmaailat3A+kXi+AkfvSj5+rm+J3q0Zs3bZqFgTxlYA/0H/w2oQ+CAQC+Qu94MJ2w2Ww22y+U91Q31fufOQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-8166-2935","institution":"Inha University","correspondingAuthor":true,"prefix":"","firstName":"Yongjin","middleName":"","lastName":"Lee","suffix":""}],"badges":[],"createdAt":"2025-07-05 13:02:30","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7053206/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7053206/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11814-025-00574-2","type":"published","date":"2025-10-07T15:57:51+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":93420031,"identity":"8614f513-c79f-4993-8f8c-fe4f5c1a2cb9","added_by":"auto","created_at":"2025-10-13 16:09:23","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1065182,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7053206/v1_covered_120ff91f-dcd6-40a6-8b1c-c729796dcbe4.pdf"},{"id":86884275,"identity":"d7b8fbc9-4921-49fa-8ad6-827a80e85cba","added_by":"auto","created_at":"2025-07-16 17:20:35","extension":"docx","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":46799,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-7053206/v1/e108093ad33ae11d795700e1.docx"}],"financialInterests":"","formattedTitle":"Advancing Vapor-Liquid Equilibrium Predictions with the OPPES United Atom Forcefield for Associating Fluids","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"korean-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"kjce","sideBox":"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)","snPcode":"11814","submissionUrl":"https://www.editorialmanager.com/kjce/default2.aspx","title":"Korean Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Subscription","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"united atom force field, Gibbs ensemble Monte Carlo simulation, associating fluids, hydrogen bonding, vapor-liquid phase equilibria","lastPublishedDoi":"10.21203/rs.3.rs-7053206/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7053206/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, we extend the OPPES united atom force field to normal alcohols, glycols, and alkoxyethanols by optimizing new potential parameters based on the previously developed OPPES n-alkane and ether models. Bonded interaction parameters were primarily adopted from the TraPPE-UA model, except for equilibrium bond lengths and bending angles, which were obtained through density functional theory (DFT) geometry optimizations. Partial charges for ether oxygens and neighboring carbon pseudo-atoms were taken from the OPPES ether model, while those for hydroxyl oxygens and hydrogens were adopted from the AMBER model. The alpha carbon's charge was determined by enforcing charge neutrality. Lennard-Jones (LJ) parameters for hydroxyl oxygen and hydrogen were fitted to experimental liquid densities and vapor pressures of representative n-alcohols.\u003c/p\u003e\u003cp\u003eUsing the optimized parameters, we performed configurational-bias Monte Carlo simulations in the NVT ensemble for five n-alcohols (methanol to 1-octanol), two glycols (1,2-ethanediol and 1,3-propanediol), and three alkoxyethanols (2-methoxyethanol to 2-propoxyethanol). 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