{"title":"Effect of confinement on water properties in super-hydrophilic pores using MD simulations with the mW model","authors":"Vikas Kumar Sinha, Chandan Kumar Das","doi":"10.1007/s00894-024-06145-2","DOIUrl":null,"url":null,"abstract":"<div><h3>Context</h3><p>We explore the influence of strongly hydrophilic confinement on various properties of water, such as density, enthalpy, potential energy, radial distribution function, entropy, specific heat capacity, structural dynamics, and transition temperatures (freezing and melting temperatures), using monatomic water (mW) model. The properties of water are found to be dependent on confinement and the wall-fluid surface interaction. Hysteresis loops are observed for density, enthalpy, potential energy, and entropy around the transition temperatures, while the size of hysteresis loops varies with confinement and surface interaction. In smaller pore sizes (<i>H</i> ≤ 20), the solid phase displays a higher density compared to the liquid phase, which is unconventional behavior compared to bulk water systems due to the pronounced hydrophilic properties of the confinement surface. Specific heat capacity exhibits more oscillations in the confined system compared to bulk water, stemming from uneven enthalpy differences across equal temperature intervals. During phase transformation in both heating and quenching processes, there is an abrupt change observed in specific heat capacity. Confinement exerts a notable impact on entropy in the solid phase, but its influence is negligible in the liquid phase. At lower pore sizes (<i>H</i> < 25 Å), there is more fluctuation in freezing temperature for all wall-fluid interactions, which diminishes beyond pore sizes of <i>H</i> > 25 Å. Similarly, more oscillatory behavior is observed in melting temperatures at lower pore sizes (<i>H</i> < 40 Å), which diminishes at higher pore sizes (<i>H</i> > 40 Å). During the quenching process, a sudden jump in the in-plane orientational and tetrahedral order parameters indicates the formation of an ordered phase, specifically a diamond crystalline structure. The percentages of different crystalline structures (cubic diamond, hexagonal diamond, and 2D hexagonal) vary with both the confinement size and the wall-fluid interaction strength.</p><h3>Methods</h3><p>Cooling and heating simulations are conducted with the mW water model using LAMMPS for different nanoscale confinement separation sizes ranging from 8.5 to 70 Å within the temperature range of 100–350 K. The water is modeled using two-body and three-body interaction potential (Stillinger–Weber potential) and the confinement is introduced using LJ 9–3 water-wall interaction potential. Entropy is calculated using RDF data obtained from the simulation experiments for each temperature point with increments or decrements of 2.5 K. The transition temperatures are estimated using the specific heat capacity analysis.</p></div>","PeriodicalId":651,"journal":{"name":"Journal of Molecular Modeling","volume":"30 10","pages":""},"PeriodicalIF":2.1000,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Molecular Modeling","FirstCategoryId":"92","ListUrlMain":"https://link.springer.com/article/10.1007/s00894-024-06145-2","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"BIOCHEMISTRY & MOLECULAR BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Context
We explore the influence of strongly hydrophilic confinement on various properties of water, such as density, enthalpy, potential energy, radial distribution function, entropy, specific heat capacity, structural dynamics, and transition temperatures (freezing and melting temperatures), using monatomic water (mW) model. The properties of water are found to be dependent on confinement and the wall-fluid surface interaction. Hysteresis loops are observed for density, enthalpy, potential energy, and entropy around the transition temperatures, while the size of hysteresis loops varies with confinement and surface interaction. In smaller pore sizes (H ≤ 20), the solid phase displays a higher density compared to the liquid phase, which is unconventional behavior compared to bulk water systems due to the pronounced hydrophilic properties of the confinement surface. Specific heat capacity exhibits more oscillations in the confined system compared to bulk water, stemming from uneven enthalpy differences across equal temperature intervals. During phase transformation in both heating and quenching processes, there is an abrupt change observed in specific heat capacity. Confinement exerts a notable impact on entropy in the solid phase, but its influence is negligible in the liquid phase. At lower pore sizes (H < 25 Å), there is more fluctuation in freezing temperature for all wall-fluid interactions, which diminishes beyond pore sizes of H > 25 Å. Similarly, more oscillatory behavior is observed in melting temperatures at lower pore sizes (H < 40 Å), which diminishes at higher pore sizes (H > 40 Å). During the quenching process, a sudden jump in the in-plane orientational and tetrahedral order parameters indicates the formation of an ordered phase, specifically a diamond crystalline structure. The percentages of different crystalline structures (cubic diamond, hexagonal diamond, and 2D hexagonal) vary with both the confinement size and the wall-fluid interaction strength.
Methods
Cooling and heating simulations are conducted with the mW water model using LAMMPS for different nanoscale confinement separation sizes ranging from 8.5 to 70 Å within the temperature range of 100–350 K. The water is modeled using two-body and three-body interaction potential (Stillinger–Weber potential) and the confinement is introduced using LJ 9–3 water-wall interaction potential. Entropy is calculated using RDF data obtained from the simulation experiments for each temperature point with increments or decrements of 2.5 K. The transition temperatures are estimated using the specific heat capacity analysis.
期刊介绍:
The Journal of Molecular Modeling focuses on "hardcore" modeling, publishing high-quality research and reports. Founded in 1995 as a purely electronic journal, it has adapted its format to include a full-color print edition, and adjusted its aims and scope fit the fast-changing field of molecular modeling, with a particular focus on three-dimensional modeling.
Today, the journal covers all aspects of molecular modeling including life science modeling; materials modeling; new methods; and computational chemistry.
Topics include computer-aided molecular design; rational drug design, de novo ligand design, receptor modeling and docking; cheminformatics, data analysis, visualization and mining; computational medicinal chemistry; homology modeling; simulation of peptides, DNA and other biopolymers; quantitative structure-activity relationships (QSAR) and ADME-modeling; modeling of biological reaction mechanisms; and combined experimental and computational studies in which calculations play a major role.