Thermodynamics Research Center

TRC supplies thermodynamic properties tables, thermophysical properties data, models, standards and research for industry, public health and safety, and the environment.

For over 70 years, TRC has produced a great number of periodical compilations and electronic databases that have become source data for scientific research and industrial process design. Subject areas include thermophysical properties and transport properties of pure compounds, binary mixtures, ternary mixtures, and chemical reactions, as well as properties for classes of materials representing particular needs in academia, industry, and government such as clathrate hydrates, and ionic liquids. The goals of TRC are to establish a comprehensive archive of experimental data of well-defined composition and be a comprehensive source of critically evaluated data.


Located in Boulder, CO, TRC Group performs several functions related to providing state-of-the-art thermodynamic data:

Critically Evaluated Data

An important and useful aspect of our work here at TRC is to provide critically evaluated data. Critical evaluation is a process of analyzing all available experimental data for a given property to arrive at recommended values together with estimates of uncertainty, providing a highly useful form of thermodynamic data for our customers. The analysis is based on intercomparisons, interpolation, extrapolation,and correlation of the original experimental data collected at TRC. Data are evaluated for thermodynamic consistency using fundamental thermodynamic principles, including consistency checks between data and correlations for related properties. While automated as much as possible, this process is overseen by experts with a great deal of experience in the field of thermodynamic data. Professional staff are responsible for the evaluation of each set of data that is committed to the archive.

For many years TRC delivered a variety of periodicals containing evaluated data for various types of chemical systems. In the last 15 years we have produced a new generation of software products implementing the concept of Dynamic Data Evaluation developed at NIST TRC, such as the NIST ThermoData Engine, Web Thermo Tables, ThermoPlan, and ThermoLit. These products are broadly used in industry, academia, and government, supporting engineering applications such as chemical process and product design, model development, and experimental planning for thermophysical property measurements.

A critical resource is our extensive in-house collection of published thermodynamic and thermophysical properties, the SOURCE data system. All of the data catalogued for critical evaluation by TRC are stored in this data system. An important aspect of TRC's mission is to continue to expand this collection to make it as complete a repository as possible for all published thermodynamic and thermophysical property data.

This comprehensive mission is the evolution of the role of TRC as a source of thermodynamic data. For information on TRC's history see:

ThermoML: XML-Based Standard for Data Storage and Exchange

Efficient and reliable data dissemination is also at the core of our work and is the driver for our development of ThermoML as a standard format for data storage and exchange. We are currently partnering with five major journals to encourage authors to submit their data for validation as part of the publication process. To further this cooperation we have created automated tools as part of the software infrastructure supporting the ThermoML standard: Guided Data Capture (GDC) provides guidance for data processing, ThermoML Opener allows direct viewing of the data and metadata contained in a ThermoML file, and ThermoML Updater automatically converts files originally formatted in accordance to the ThermoML Recommendations 2006 to formats correspoding to the ThermoML Recommendations 2011. All data submitted to NIST TRC through participating journals are publically available through our ThermoML Archive.

ThermoML is a new standard for thermodynamic data communication that was initially developed within IUPAC Project 2002-055-3-024: XML-based IUPAC Standard for Experimentally and Critically Evaluated Thermodynamic Property Data Storage and Capture, and later extended under the IUPAC project 2007-039-1-024: Extension of ThermoML - the IUPAC Standard for Thermodynamic Data Communications. The namespace, ThermoML, has been reserved by IUPAC.

TDE: ThermoData Engine

NIST TRC created the ThermoData Engine (NIST TDE), the first software product implementing the concept of dynamic data evaluation. This concept was itself formulated at NIST TRC. TDE is available in two editions: Standard Reference Database 103a - ThermoDataEngine - Pure Compounds only, and Standard Reference Database 103b - ThermoDataEngine - Pure Compounds, Binary Mixtures, Ternary Mixtures, and Chemical Reactions. The ThermoData Engine software provides critically evaluated thermodynamic and transport property data on demand using an expert system to extract data from the TRC Source data archive.

WTT: Web Thermo Tables

This product provides the most up-to-date source for critically evaluated thermodynamic data. It is available in two versions: a Professional Edition and a Lite Edition. Both are available by subscription through the NIST Standard Reference Data program (SRD). WTT - Professional Edition represents a complete collection of critically evaluated thermodynamic property data primarily for pure organic compounds. As of November, 2011, WTT contains information on 23,399 compounds. WTT - Lite Edition represents a collection of critically evaluated thermodynamic property data for 150 commonly-used (primarily organic) pure compounds.


The ThermoPlan web application provides support for experimental planning. It provides free and open access for the broader research community to the experimental planning utilities that are incorporated into ThermoData Engine (TDE). TDE provides recommendations for the relative merit of a proposed measurement via assessment of the existing body of knowledge, including availability of experimental thermophysical property data, variable ranges studied, associated uncertainties, state of prediction methods, and parameters for deployment of prediction methods. The web applications provides utilities for the assessment of specific property measurements for pure and binary chemical systems, the broader data needs of pure systems, and recommendations for binary mixture measurements that could extend the current UNIFAC model.

The primary focus of this recommendation service is molecular organic compounds. Some common inorganic and organometallic compounds are included, but, in general, polymers, radicals, ions, salt and acid solutions, metals, metal oxides, and inter-metallics are not considered.


The ThermoLit web application provides free and open access to literature information contained in the NIST SOURCE Data Archive [Int. J. Thermophys., 2012, Vol. 33, No. 1, p. 22-33.] and provides an easy-to-use tool for generation of a NIST Literature Report in PDF format. The tool is intended to aid researchers and reviewers in determining relevant literature sources for a given thermophysical property measurement; however, it is not intended to replace the comprehensive literature review required by all journals, and no guarantee is made regarding completeness of the information provided. The primary focus of this service is molecular organic compounds. Some common inorganic and organometallic compounds are included, but, in general, polymers, radicals, ions, salt and acid solutions, metals, metal oxides, and inter-metallics are not considered.