Simbody
3.7

These are preprocessor (#define) macros providing constants values at very high precision. See the discussion under the main Predefined Constants module heading. More...
Modules  
Mathematical Constants  
These are some common unitless numerical constants evaluated to 64 digits and written here in maximal (long double) precision.  
Physical Constants  
These constants are from the CODATA 2002 set from the NIST Physics Laboratory web site http://physics.nist.gov/constants (NIST SP 961 Dec 2005).  
Unit Conversion Factors  
In each case here, given a value in the units mentioned first in the name, you should multiply by the given constant to produce the equivalent quantity measured in the units that appear second in the name.  
These are preprocessor (#define) macros providing constants values at very high precision. See the discussion under the main Predefined Constants module heading.
Our most common unit systems are the "SI" (MKS) system, and the "MD" system used for molecular dynamics. SI units are meters, kg, seconds, coulombs (amperes), kelvins and moles. MD units are nanometers, atomic mass units (Daltons, g/mol), picoseconds, proton charge e, kelvins, and moles. Many molecular dynamicists and chemists prefer kcals for energy and angstroms for length. This does not constitute a consistent set of units, however, so we provide for it by conversion from the MD units, which are consistent. (By consistent, we mean that force units = masslength/time^2, so f=ma!)
Unit systems
SI (MKS) MD KCALANGSTROM     length meter nanometer angstrom (A) mass kg amu, dalton amu, dalton time second picosecond picosecond charge coulomb e, proton charge e, proton charge temp. kelvin kelvin kelvin substance mole mole mole
velocity m/s km/s (nm/ps) 100m/s (A/ps)
energy J (kgm^2/s^2) kJ/mol kcal/mol (Danm^2/ps^2) (418.4 DaA^2/ps^2) force N (kgm/s^2) kJ/(molnm) = TN/mol kcal/(molA) (Danm/ps^2) (T=10^12) (418.4 DaA/ps^2)
We always keep angles in radians internally, which are unitless. However, most humans prefer degrees where 1 degree = Pi/180 radians so we provide convenient conversions.