NIST Standard
Reference Database 88
NIST/TRC
Ideal Gas Database
Version 2.0
Users'
Guide
Data
compiled and evaluated by:
NIST
Physical
and Chemical Properties Division
October 2006
Technology
Administration
National
Standard
Reference Data Program
The National Institute of Standards and Technology (NIST)
uses its best efforts to deliver a high-quality copy of the database and to
verify that the data contained therein have been selected on the basis of sound
scientific judgment. However, NIST makes
no warranties to that effect, and NIST shall not be liable for any damage that
may result from errors or omissions in the database.
COPYRIGHT (C) 2006 copyright by the U.S. Secretary of Commerce on behalf of the
ACKNOWLEDGMENTS
The NIST/TRC
Ideal Gas Database is companion software to the book:
"Thermodynamics
of Organic Compounds in the
This package contains the NIST/TRC Ideal Gas
Database (TRCIGD).
1. INTRODUCTION
1.1 Database Description
The
NIST TRC Ideal Gas database (TRCIGD) provides information on the most important
thermodynamic properties (heat capacities, entropies, enthalpies, Gibbs free
energies and enthalpies and Gibbs free energies of formation) of organic (and
some other) compounds in the ideal gas state. The database contains a total of
more than 2000 compounds. The heat capacities are calculated using coefficients
of linear or non-linear functions of their temperature dependence. These
coefficients were obtained based on the results of statistical mechanical or
additive calculations. The other properties (entropies, enthalpies and Gibbs
free energies) are determined by integration using a heat capacity function.
The enthalpies and Gibbs free energies of formation are calculated based on the
properties of the individual compounds and the properties of their elements in
the standard states. The calculations can be performed in two different
regimes: NON-LINEAR and POLYNOMIAL. The regime POLYNOMIAL uses a linear
function to represent temperature dependence of heat capacity. This function is
simple and commonly used in engineering applications. However, there may not be
a sufficient number of significant digits to insure sufficient accuracy at
temperatures higher than 3000 K. When choosing the NON-LINEAR regime, the heat
capacities are calculated using the non-linear function of temperature. This
function is quite complicated, but it ensures sufficient accuracy over a wide
temperature range. The NON-LINEAR regime is the default selection when the user
starts running this database. The new version 2.0 is run by new window
interface.
1.2 Installation
To
install the NIST TRC Ideal Gas Database (TRCIGD) on your hard drive, insert the
CD-Rom, go to Start/Run and click on the program setup.exe.
1.3 System Requirements:
The
program requires Pentium processor, ®Windows 2000 or XP, and at least 64 Mb memory (256 recommended).
2. Use of the
Program
2.1 Selection
of Compounds
Multiple
compounds can be selected and accumulated in a list. To add a compound, CLICK
the “Add compound” button and enter any combination of CAS registry number,
formula (partial formula) and name (partial name) on the compound selection
form.
(1)
Enter Empirical Formula and/or Name:
(A)
Empirical Formula
0Enter the entire empirical formula
1(e.g., C5H5N, (NH2)2CO )
(B)
Name
0Enter the entire name or use
wildcards (*)
1(e.g., 2-methylpyridine, 2-methylp*,
2-*-pyridine)
(2)
CLICK “Find” to complete the search
(A)
If the compound appears in the list
0Select the compound from the list and
1CLICK "Accept"
(3)
Repeat (1)-(2) to add another compound or CLICK “Done"
NOTE:
Symbols for elements are case sensitive (e.g., use “Br” and not ”BR” or ”br”
for bromine)
Compounds can be removed from the
list by pressing the Delete key. The compound list can be cleared by clicking
the “Clear compounds” button.
2.2 Selection of Temperatures
Selected
temperatures are accumulated in a list. To add temperatures, CLICK the Add
temperature button and enter temperatures separated by spaces and/or a
temperature range specified by the lower temperature, higher temperature, and
temperature step on the temperature-selection form.
Temperatures
can be removed from the list by pressing the Delete key. The temperature list
can be cleared by clicking the “Clear T” button.
2.3 Selection of Equations
To
complete the request, CLICK either the “Get data (linear equation)” or “Get
data (non-linear equation)” button.
The
mathematical forms of the equations are given later in this Help.
2.4 Saving the Data
The
data can be saved in a file through the menu File->Save or by pressing the
Ctrl-S key combination. Otherwise, all or any part of the results can be
highlighted and copied to the system clipboard by pressing Ctrl-C.
3. Output Specifications
The output consists of 7 columns; the last two are present
if the enthalpy of formation is available.
|
T (K) |
Temperature |
|
Cp (J/K/mol) |
Heat capacity at constant pressure |
|
S (J/K/mol) |
Absolute entropy |
|
(H-H0)/T (J/K/mol) |
Reduced enthalpy (divided by temperature); reference state
is ideal gas at T = 0 K |
|
-(G-H0)/T (J/K/mol) |
Negative reduced Gibbs energy (divided by temperature);
reference state is ideal gas at T = 0 K |
|
HForm (kJ/mol) |
Enthalpy of formation |
|
GForm (kJ/mol) |
Gibbs energy of formation |
Note: All
values correspond to 1 bar pressure.
Parameters αi,
I, J of smoothing equations used to generate the tabulated data
along with their ranges of validity are also included in the output. The
equations are described later in this Help.
UNCERTAINTIES. As traditionally published, the values of the
calculated heat capacities, entropies, reduced enthalpies, and reduced Gibbs
energies are represented with two decimal places while enthalpies and Gibbs
energies of formation are displayed with one decimal place. The uncertainties
of the calculated thermodynamic functions are estimated to be around 1% . This
estimate does not include the uncertainties related to the contributions
associated with the selection of the models for anharmonicity, existence of the
tautomers and conformers as well as complex internal rotations.
4. Smoothing equations
Two smoothing equations are used in this database to
represent ideal-gas heat capacities and derived properties as functions of
temperature, linear and non-linear. You can choose one of them at a time.
Linear equation works in a restricted temperature range, usually below or above
1000 K, so generally two linear equations smoothly connecting at certain
temperature are provided for each compound in the database. Non-linear equation
covers the whole temperature range for a compound.
4.1 Linear equation
where
ideal-gas heat capacity
(H0(T) - H0(0)) enthalpy (reference state is ideal
gas at T = 0 K)
S0(T) absolute entropy at temperature T and P0 = 1 bar
R
gas constant
T
temperature
αi, I, J equation parameters
4.2 Non-linear equation
with
if T > a7; 0 if
T <= a7
with
if T > a7; 0 if T <= a7
with
if T > a7; 0 if T <= a7
where
ideal-gas heat capacity
(H0(T) - H0(0)) enthalpy (reference state is ideal
gas at T = 0 K)
S0(T) absolute entropy at temperature T and P0 = 1 bar
R
gas constant
T
temperature
αi, I, J equation parameters
The equations are also described in the literature:
Michael
Frenkel, G.J.Kabo, K.N.Marsh, G.N.Roganov, and R.C.Wilhoit
Thermodynamics
of Organic Compounds in the
ISBN
1-883400-04-X
Linear equation: Equation 3.34, Page 539.
Non-linear
equation: Equation 3.30, Page 537.
5. Reference
Michael Frenkel, G.J.Kabo, K.N.Marsh, G.N.Roganov, and R.C.Wilhoit
Thermodynamics
of Organic Compounds in the
ISBN
1-883400-05-8
CONTACTS
The scientific contact for the database is:
Dr. Michael Frenkel, Director
NIST Physical and Chemical Properties Division (838)
325 Broadway Mailcode 838.00
frenkel@boulder.nist.gov
Phone: (303) 497-3952
If you have questions or comments about the database, Standard Reference Data would like to hear from you. Also, if you have any problems with the diskettes or installation, please let us know by contacting:
Joan
Sauerwein
National
Standard
Reference Data
Internet:
http://srdata.nist.gov/contact/contact
FAX:
(301) 926-0416
Phone:
(301) 975-2208
