Improving force field accuracy by training against condensed phase mixture properties

2021 ◽  
Author(s):  
Simon Boothroyd ◽  
Owen Madin ◽  
David Mobley ◽  
Lee-Ping Wang ◽  
John Chodera ◽  
...  
Keyword(s):  
Force Field ◽  
Physical Property ◽  
Liquid Mixtures ◽  
Pure Liquid ◽  
Full Potential ◽  
Field Representation ◽  
Biological Phenomena ◽  
Liquid Systems ◽  
Fundamental Insight ◽  
Physical Property Data

Developing a sufficiently accurate classical force field representation of molecules is key to realizing the full potential of molecular simulation as a route to gaining fundamental insight into a broad spectrum of chemical and biological phenomena. This is only possible, however, if the many complex interactions between molecules of different species in the system are accurately captured by the model. Historically, the intermolecular van der Waals (vdW) interactions have primarily been trained against densities and enthalpies of vaporization of pure (single-component) systems, with occasional usage of hydration free energies. In this study, we demonstrate how including physical property data of binary mixtures can better inform these parameters, encoding more information about the underlying physics of the system in complex chemical mixtures. To demonstrate this, we re-train a select number of the Lennard-Jones parameters describing the vdW interactions of the OpenFF 1.0.0 (Parsley) fixed charge force field against training sets composed of densities and enthalpies of mixing for binary liquid mixtures as well as densities and enthalpies of vaporization of pure liquid systems, and assess the performance of each of these combinations. We show that retraining against the mixture data almost universally improves the force field's ability to reproduce both pure and mixture properties, reducing some systematic errors that exist when training vdW interactions against properties of pure systems only.

scholarly journals Improving force field accuracy by training against condensed phase mixture properties

2021 ◽  
Author(s):  
Simon Boothroyd ◽  
Owen Madin ◽  
David Mobley ◽  
Lee-Ping Wang ◽  
John Chodera ◽  
...  
Keyword(s):  
Force Field ◽  
Physical Property ◽  
Liquid Mixtures ◽  
Pure Liquid ◽  
Full Potential ◽  
Field Representation ◽  
Biological Phenomena ◽  
Liquid Systems ◽  
Fundamental Insight ◽  
Physical Property Data

Developing a sufficiently accurate classical force field representation of molecules is key to realizing the full potential of molecular simulation as a route to gaining fundamental insight into a broad spectrum of chemical and biological phenomena. This is only possible, however, if the many complex interactions between molecules of different species in the system are accurately captured by the model. Historically, the intermolecular van der Waals (vdW) interactions have primarily been trained against densities and enthalpies of vaporization of pure (single-component) systems, with occasional usage of hydration free energies. In this study, we demonstrate how including physical property data of binary mixtures can better inform these parameters, encoding more information about the underlying physics of the system in complex chemical mixtures. To demonstrate this, we re-train a select number of the Lennard-Jones parameters describing the vdW interactions of the OpenFF 1.0.0 (Parsley) fixed charge force field against training sets composed of densities and enthalpies of mixing for binary liquid mixtures as well as densities and enthalpies of vaporization of pure liquid systems, and assess the performance of each of these combinations. We show that retraining against the mixture data almost universally improves the force field's ability to reproduce both pure and mixture properties, reducing some systematic errors that exist when training vdW interactions against properties of pure systems only.

Spatial scale effects on model parameter estimation and predictive uncertainty in ungauged basins

2012 ◽  
Vol 44 (3) ◽  
pp. 441-453 ◽  
Author(s):  
Denis A. Hughes ◽  
Evison Kapangaziwiri ◽  
Jane Tanner
Keyword(s):  
Parameter Estimation ◽  
Spatial Scale ◽  
Scale Effects ◽  
Physical Property ◽  
Hydrological Modelling ◽  
Ungauged Basins ◽  
Estimation Equations ◽  
Property Data ◽  
Physical Property Data ◽  
Parameter Values

The most appropriate scale to use for hydrological modelling depends on the model structure, the purpose of the results and the resolution of available data used to quantify parameter values and provide the climatic forcing. There is little consensus amongst the community of model users on the appropriate model complexity and number of model parameters that are needed for satisfactory simulations. These issues are not independent of modelling scale, the methods used to quantify parameter values, nor the purpose of use of the simulations. This paper reports on an investigation of spatial scale effects on the application of an approach to quantify the parameter values (with uncertainty) of a rainfall-runoff model with a relatively large number of parameters. The quantification approach uses estimation equations based on physical property data and is applicable to gauged and ungauged basins. Within South Africa the physical property data are available at a finer spatial resolution than is typically used for hydrological modelling. The results suggest that reducing the model spatial scale offers some advantages. Potential disadvantages are related to the need for some subjective interpretation of the available physical property data, as well as inconsistencies in some of the parameter estimation equations.

Thermodynamic properties of liquid mixtures: Selection of the pure liquid parameter

1974 ◽  
Vol 27 (3) ◽  
pp. 647 ◽  
Author(s):  
DV Fenby ◽  
NF Pasco
Keyword(s):  
Equation Of State ◽  
Thermodynamic Properties ◽  
Equations Of State ◽  
Liquid Mixtures ◽  
Pure Liquid ◽  
Excess Thermodynamic Properties ◽  
Pure Fluids ◽  
Liquid Parameter ◽  
Selection Of

There has recently been a revival of interest in theories of liquid mixtures based on analytic equations of state for pure fluids. We have shown that the method used to determine the parameters of the pure-liquid equation of state has a significant effect on the excess thermodynamic properties obtained from such theories.

scholarly journals Current Status of AMOEBA–IL: A Multipolar/Polarizable Force Field for Ionic Liquids

2020 ◽  
Vol 21 (3) ◽  
pp. 697
Author(s):  
Erik Antonio Vázquez-Montelongo ◽  
José Enrique Vázquez-Cervantes ◽  
G. Andrés Cisneros
Keyword(s):  
Ionic Liquid ◽  
Force Field ◽  
Decomposition Analysis ◽  
Lanthanide Ions ◽  
Current Status ◽  
Energy Decomposition Analysis ◽  
Quantum Mechanical ◽  
Exchange Reactions ◽  
Polarizable Force Field ◽  
Liquid Systems

Computational simulations of ionic liquid solutions have become a useful tool to investigate various physical, chemical and catalytic properties of systems involving these solvents. Classical molecular dynamics and hybrid quantum mechanical/molecular mechanical (QM/MM) calculations of IL systems have provided significant insights at the atomic level. Here, we present a review of the development and application of the multipolar and polarizable force field AMOEBA for ionic liquid systems, termed AMOEBA–IL. The parametrization approach for AMOEBA–IL relies on the reproduction of total quantum mechanical (QM) intermolecular interaction energies and QM energy decomposition analysis. This approach has been used to develop parameters for imidazolium– and pyrrolidinium–based ILs coupled with various inorganic anions. AMOEBA–IL has been used to investigate and predict the properties of a variety of systems including neat ILs and IL mixtures, water exchange reactions on lanthanide ions in IL mixtures, IL–based liquid–liquid extraction, and effects of ILs on an aniline protection reaction.

X-Ray Diffraction Studies on the Titanium-Nickel System

1962 ◽  
Vol 6 ◽  
pp. 74-84
Author(s):  
John V. Gilfrich
Keyword(s):  
Heat Treatment ◽  
Room Temperature ◽  
Stoichiometric Composition ◽  
Physical Property ◽  
X Ray Diffraction ◽  
X Ray ◽  
Property Data ◽  
Before And After ◽  
Titanium Nickel ◽  
Physical Property Data

AbstractX-ray diffraction studies were made on the Ti–Ni system around the stoichiometric composition of the intermetallic compound TiNi to clarify some confusion which has existed about the phase diagram in this region, and to explain some anomalies in the physical properties of this material. Wrought and cast samples were examined at room temperature both before and after heat treatment and at temperatures both above and below ambient. The compound TiNi does exist at room temperature. The phase purity of the particular sample was found to be greatly affected by such factors as minor variations in composition, heat treatment, and method of sample preparation. Some confirming metallographlc and physical property data will also be presented.

Surface Modified Boehmite Aluminas: A Versatile Approach to Nano-scale Particle Dispersion and Nanocomposites

2005 ◽  
Vol 879 ◽  
Author(s):  
Steven L. Baxter
Keyword(s):  
Particle Size ◽  
Physical Property ◽  
Particle Dispersion ◽  
Aqueous Systems ◽  
Nano Scale ◽  
Organic Matrices ◽  
Crystallite Sizes ◽  
Scale Particle ◽  
Physical Property Data ◽  
Surface Modified

AbstractCertain forms of monohydrate aluminum oxide, commonly known as boehmite or pseudoboehmite alumina, are known to disperse in water at low pH to nano-scale dimensions. The upsurge of interest in nano-scale structures has prompted our study of the surface modification of nano-scale boehmite aluminas with organic acids in order to achieve dispersion of these materials in non-aqueous systems and alkaline aqueous systems.This paper discusses the variety of modifiers used to achieve compatibilization and dispersion of nano-sized particles of these boehmite aluminas in aqueous and organic matrices. Organic modification of a variety of crystallite sizes (5-60 nm) and shapes (plates, needles, blocks) has been achieved, including materials of high aspect ratio. We describe the properties of these dispersions, including primary particle size, dispersed particle size, and surface charge. Finally, we present physical property data of polymer nanocomposites prepared from these materials. These materials are based on a commercial process which has been in operation for over 40 years and which has global production capacities of 70,000 tons per annum.

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