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The Division’s work is structured along four synergistic themes. A brief summary of recent highlights and more detailed discussions can be found by following the indicated links.
..I. Measurement System Support : provide the measurement capabilities, reference materials and reference data needed to underpin a national system of physical and chemical properties measurements;
.II. Archived and Evaluated Property Data : develop large-scale, readily accessible data resources providing trustworthy physical and chemical properties information;
III. Prediction of Property Information: develop theoretical and computational predictive capabilities to enable reliable estimation of property values when experimental data are unavailable.IV. Measurements for Special Applications : research experimental techniques and address key data-gaps in support of specific, high priority industrial and national initiatives.
Currently a project to develop world class density measurement capabilities is coming to fruition with new benchmark measurements for propane. A reference equation of state has been developed that agrees with all high quality experimental determinations to within less than 100 ppm and with the recent NIST measurements to within approximately 20 ppm. A novel and potentially important application of the new density measurement apparatus in determining thermodynamic temperature also was explored this year. This work is described in highlight Precision Densimetry for Primary Temperature Metrology .
Reference equations of state developed by the Division have often served as the basis for important international agreements on physical properties. This year the International Standards Organization (ISO) adopted the equations of state used in the NIST REFPROP 7 Database as the basis for a new international standard for the properties of refrigerants. This work, as well as other advances in high accuracy equations of state, is described in highlight Reference Equations of State.
The Division has a wide spectrum of activities focused on collecting and evaluating published data to produce high quality resources for properties information. Perhaps the most famous is The NIST Chemistry WebBook. This website has been awarded "Best Chemistry Site on the Web - Portals and Information Hubs" by ChemIndustry.com Inc., John Wiley and Sons, Inc. and the Royal Society of Chemistry, UK. The WebBook is second in total use among chemistry database web sites (only the Chemical Abstracts site has higher usage) and over 2,500 sites directly link to the WebBook, including essentially every technical library in the world., such as those listed above. This year the Chemistry WebBook has been made available in other language versions, cf. the highlight The NIST Chemistry WebBook Goes Multilingual.
In recent years, the Division’s TRC Group has established a truly new paradigm in data collection, data quality specification, and data exchange standards. The new approach in data collection involves direct collaborations with journal editors and submitting authors such that after the acceptance of a manuscript, but prior to its publication, all the contained data are submitted to TRC using the TRC Guided Data Capture tool (http://www.trc.nist.gov/GDC.html). TRC subjects the submitted data to checks for specification of all required metadata, the information describing the experiment and the data itself, and for internal consistency. Communication with the authors is used to resolve any consistency or specification issues. Following correction (if necessary) the data are returned to the author and journal editor in ThemoML, the XML standard for exchange of thermodynamic data. At the time of publication, the data are made available on the TRC website (http://www.trc.nist.gov/ThermoML.html) and become part of the TRC SOURCE Database.(SOURCE is the world’s largest collection of experimental data covering thermodynamic, thermochemical, and transport properties for pure compounds and mixtures of well-defined composition. Over 300,000 data points are added to the collection each year.)In the coming year, collaborations will be established with all 5 major journals publishing thermodynamic data and TRC SOURCE will be maintained current with approximately 80% of all new data appearing in the literature.
The Division has embarked on another collaborative data project this past year, in this case a collaboration to facilitate the collection of data describing the pathways and rates of chemical reactions. In this project, described in the highlight Combustion Simulation Databases for Real Transportation Fuels: A New Community Collaboration, the Division has joined with the combustion research community, in an organization called the PrIMe Initiative, to create a central repository of all information needed to support the use of combustion models for design and optimization of the next generation of gasoline and diesel engines. As part of this effort, the collaboration is developing specifications and exchange standards for the relevant data, this standard is termed ReactionML.
Data exchange and interoperability infrastructure is required to support widespread and effective use of physical and chemical property information. ThermoML and ReactionML are examples of two of the standards that the Division is helping the community develop and adopt. This year, ThermoML was accepted as the foundation for an IUPAC (International Union of Pure and Applied Chemistry) standard for global communication of thermodynamic data; see the highlight ThermoML – an Emerging IUPAC Standard for Thermodynamic Data Communications .
Another major achievement this year was the release of the beta-version of the IUPAC-NIST Chemical Identifier (INChI). This is a naming system that would allow computers to search for and uniquely identify a chemical based entirely on the connectivity of the molecule – that is what atoms are connected to what other atoms. There is enormous value in this identifier for unambiguous and efficient web searches for chemical data. Its design is discussed in the highlight The IUPAC NIST Chemical Identifier (INChI)
In another international collaboration, the Division is working to develop standards for measuring, specifying, and archiving property data for ionic liquids. Some highlights of this work are presented in IUPAC Partnership Develops Standards and a Data Retrieval System for Ionic Liquids.
Other important highlights of this years work in theme II deal directly with the provision of property data. A series of papers were published this year describing, for the first time, the transport properties of the heavier linear alkanes commonly present in fuels. The primary approach in this work is the critical assessment of all available experimental data and their representation by models capturing correlations in the properties and incorporating fundamental theory where possible. This work is described in the highlight Integrated Transport Property Program for Key Systems: Data, Models, and Simulation. This work complements another project focused on fuels discussed below under theme IV, “Measurements for Special Applications”.
The highlight ThermoData Engine: New Generation Expert System for Thermodynamic Data Critical Evaluation describes an important first, i.e. the realization of expert system software that captures principal elements of the “art of data evaluation”. This software/database system, called TDE, is a major step toward the idea of on-demand generation of evaluated property values based on a comprehensive and up-to-date data archive (SOURCE), a process termed “dynamic data evaluation”. In addition to relying on all the infrastructure to create and maintain the SOURCE archive, this research includes development of algorithms and computer codes for assessment of the quality of existing data, for selection and application of prediction methods depending on the chemical structure of the compound and nature of the property, for establishing consistency amongst all property values, and for arriving at a recommended value with an uncertainty accurately representing all that is known at the present time.
As the Division continues to increase the information-base in physical and chemical properties, its research creates concomitant gains in understanding these properties and in the science base that allows making reliable estimates of their values. In performing its function, TDE uses much of the current state of the art in estimation. High accuracy equations of state and pure substance correlations also are used as the first step in estimating properties for substances and conditions which have not yet been measured. The Division also maintains a significant effort in computational physics and chemistry to develop practical, first-principles based approaches to understanding and predicting physical and chemical properties.
The major accomplishments in the area of first principles prediction of fluid properties are presented in three highlights.The work reported in Theory of Non-Bonded Interactions: Molecular Association and Assembly explores accurate and practical approaches to quantum calculations of intermolecular forces (the basis for describing bulk properties) and methods for reliable and efficient molecular simulation of bulk properties. It has been shown that a computationally efficient approach to calculating intermolecular forces, the Hartree-Fock Dispersion method, developed by the research team provides results in good agreement with experiment and overcomes major short-comings of more conventional computational methods. A very promising result has come from research that addresses efficient methods to calculate bulk properties; in this case mixture phase behavior. An innovative and extremely efficient simulation method, transition matrix Monte-Carlo, has been shown to accurately predict an entire isothermal fluid-phase diagram in a single simulation requiring far less CPU time than currently used techniques. The work discussed in Transport Coefficients and Molecular Dynamics is a preliminary, systematic comparison of various approaches to calculating transport properties. The Division in collaboration with scientists from The Dow Chemical Company, BP Amoco Chemical Company, Case Scientific, Mitsubishi Chemical Corporation, 3M Company, and DuPont has conducted the Second Industrial Fluid Properties Simulation Challenge. The goal of the “Challenge” is to evaluate and benchmark available molecular simulation methods and force fields on problems that have significant industrial relevance. The most recent “competition”, described in Second Industrial Fluid Properties Simulation Challenge, was very successful and attracted significantly increased interest and industry involvement.
The highlight Systematic Validation and Improvement of Quantum Chemistry Methods for the Prediction of Physical , and Chemical Properties reports new results quantifying uncertainties in properties computed by the most popular levels of theory making use of standard statistical techniques and high quality experimental data. This work is also focused on making available procedures and data that will enable researchers in industry to choose the most reliable quantum chemistry methods for prediction of physical and chemical properties.
Methods developed recently which allow computational chemistry to deal with surface-fluid interface for realistic conditions as encountered in chemical processing or the environment have born fruit in a recent collaborations to understand the surface chemistry of hematite. This work is described in highlight Computational Chemistry Illuminates Atomistic Processes at Complex Interfaces.
The staff of the Physical and Chemical Properties Division provide regular updates and supplements to reference data collections and series, and numerous book chapters updating the state of the art across a wide spectrum of customer interests. Of particular note this year are chapters titled: “The Development and Application of Cryocoolers Since 1985” and “Refrigeration for Superconductors”, see the highlight Properties and Processes for Cryogenic Refrigeration.
The Division determined key data for a number of important national agendas this past year. As part of its efforts to support programs to improve the performance of engines which rely on practical (complex) transportation fuels, the Division measured thermophysical properties of RP-1, a rocket fuel. RP-1 is being considered as a fuel for advanced aerospace engines. The work is described in the highlight Advanced Propulsion Systems Demand Accurate Property Data.
Concerns in the area of homeland security motivate work related to the detection of explosives which is highlighted in Explosives on Surfaces: A Sticky Problem. The most extensive data generation effort in the Division provides a large volume of high quality, evaluated mass spectra of molecules, known as the NIST/EPA/NIH Mass Spectral Library. This library is included and its associated search capabilities are installed by manufactures in the vast majority of mass spectrometer systems sold in the world. To assure the quality of these libraries, search and identification algorithms are developed by the Division. This software system, termed AMDIS, is optimized for the analysis of weak features in the spectrum, easily considered “noise”. Recent developments in this area are reported in the highlight AMDIS – Automatic Mass spectral Deconvolution and Identification Software. This extremely powerful software is widely employed for highly sensitive and reliable identification of threat agents by mass spectroscopy in the area of homeland security.
AMDIS is based the Division’s expert knowledge about the paths and probabilities of molecular excitation and fragmentation associated with electron impact ionization. This year the Division embarked on a new research effort to develop a similar high-level of understanding concerning the fragmentation of peptide ions undergoing collisions in MS/MS instruments. The goal is to develop reference peptide fragmentation mass spectra, physically based fragmentation rules which account for differences in instrument design and operating characteristics, and deconvolution/identification software, analogous to AMDIS. MS/MS spectroscopy is a mainstay of the analytical tools employed in the extremely important and challenging national effort in proteomics. This pioneering work is described in the highlight Mass Spectroscopy in Health and Environmental Science.
Another research effort in the area of mass spectroscopy seeks to achieve orders of magnitude improvements in the speed and sensitivity achievable with electron impact time of flight mass spectrometry. The approach is based on a Hadamard modulation of the ionizer voltage at very high frequencies; see the highlight Invention of a New Class of Ultra-fast, Ultra-sensitive Mass Spectrometers for Kinetics, Reference Mass Spectrometry, and Homeland Defense Applications.
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Last modified: 29 February 2000
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