Constants

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Introduction

There are a number of constants used in SysCAD in calculations, models or the solver. Wherever possible the references used are obtained from NIST website.

Conversions

For constants used in converting between different units of measurement see Conversion Factors.

Reference: NIST - Guide for the Use of the International System of Units (SI) (NIST Special Publication 811 2008 Edition, Ambler Thompson and Barry N. Taylor).

Molecular Weights

The Standard Atomic Weights are used to define the molecular weight of species. Please see Species Definition.

The Standard Atomic Weights are taken from NIST, except for the following elements which have updated using latest information from IUPAC.

Al, As, Au, Be, Cd, Co, Cs, F, Ge, Hf, Hg, Ho, Mn, Mo, Nb, P, Pr, Rh, Sc, Se, Tb, Th, Tm, Y, Yb

References:

1. Standard Atomic Weights. Reference NIST Version 3.0 July 2010 (M.E. Weiser, M. Berglund, et al).
2. Atomic weights of the elements 2013 (IUPAC Technical Report)
3. Standard Atomic Weight Of Ytterbium Revised 2015
4. Standard Atomic Weights Of 14 Chemical Elements Revised 2018
5. Standard Atomic Weight Of Hafnium Revised 2019

Other Constants

Some other constants used in SysCAD.

Constant	Value	Units	Reference
Gravitational Constant	9.80665	m/s2	NIST
Universal Gas Constant	8.314472	J/mol K	NIST
PI	3.14159265358979
Standard Temperature	25.0	°C
Standard Pressure	101.325	kPa

Use in PGM

Constants can be accessed directly in MP and PGM code. See Predefined Constants.

For molecular weights use PGM Species Database Class and MW() function.