Prediction of 1-Octanol-Water Partition and Infinite-Dilution Activity Coefficients

Objective:

The objective of this Challenge of the IFPSC is to test the ability of computer modeling (any method) to predict 1-Octanol-Water Partition (ko/w) and Infinite-Dilution Activity Coefficients (gam-inf). Prediction of 1-Octanol-Water Partition Coefficients (which, admittedly, has been widely studied by non-molecular simulation computational methods) is viewed as a stepping stone to a more difficult problem, such as a case where a third component is present at a high enough level to influence the mutual solubilities of the other two.

This is a proposal for the 5th Industrial Fluid Properties Simulation Challenge problem. Please send you feedback and sugestions to ifpsc@fluidproperties.org by February 15, 2008.

Prediction of 1-Octanol-Water Partition and Infinite-Dilution Activity Coefficients

Objective:

The objective of this Challenge of the IFPSC is to test the ability of computer modeling (any method) to predict 1-Octanol-Water Partition (ko/w) and Infinite-Dilution Activity Coefficients (gam-inf).

Background:

The culmination of the 4th Industrial Fluid Properties Simulation Challenge occurred at a session on November 8 at the AIChE annual meeting in Salt Lake City, Utah. Announced in San Francisco in November of 2006, the IFPSC challenged entrants to calculate a wide range of thermodynamic and transport properties for new molecular models of ethylene oxide at 375 K. Five teams accepted the challenge and were judged based on the comparison of the properties of their new models to a set of benchmark data. Participants were honored at the AIChE session with plaques and cash prizes and gave presentations describing their work.

These days it seems that molecular simulation papers are appearing in almost every scientific journal, and the documentation of these simulation methods in not always of consistently high quality. Therefore, the IFPSC wants to create a checklist of sorts for authors to use when writing papers and for reviewers to use when evaluating papers to help improve the overall quality of the scientific literature in this field. At the IFPSC workshop at 3M during the fall of 2006, Wilfred van Gunsteren and Ray Mountain developed a first draft of such criteria given below.

We invite you to review these criteria and make comments to improve them. What needs to be added? What is essential? What is only "nice-to-have?" etc.

The scoring spreadsheet for the 4th Industrial Fluid Properties Simulation Challenge (IFPSC) is now available: link

More information about the 4th Challenge is available here: link

Please note that there are some typos in the paper by Wielopolski and Smith describing the "round-robin" model used as part of the 4th simulation challenge.

On page 471, the oxygen charge should be -0.3216.

On page 472, the Lennard-Jones size paramter σ(O-O) is incorrectly labeled as a mixed interaction σ(O-C). It is actually the oxygen size parameter.

Introduction and Background

Researchers working in an industrial setting are commonly asked to predict a wide range of physical properties. A method that is able to predict a broad range of properties (especially properties that were not used in the original model parameterization) may be more valuable in this situation than a method that may provide more accurate results but only for one property or property type.

The primary objective of the Fourth Industrial Fluid Properties Simulation Challenge is to test the transferability of methods and force fields to a wide variety of properties for a given small molecule. There will be two categories of competition: 1) "molecular simulation" methods and 2) "other methods." A champion will be announced for each of the two categories.

State Conditions Transferability

For the "State Conditions Transferability" problem, nine groups from government and academic laboratories around the world had attempted to predict bubble pressures for mixtures of 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea refrigerant) and ethanol at 343 K. They had been provided with data for the system at 283K. Extrapolation from an experimentally known state condition to an unknown can be very difficult. A few methods for this kind of problem have been developed for pure component properties, but most industrial systems are mixtures. Standard models in process engineering typically do not perform well for this task.