Preprocessor Macro Constants

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.

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Detailed Description

These are preprocessor (#define) macros providing constants values at very high precision. See the discussion under the main Predefined Constants module heading.

Units

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 (ampere-s), 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 = mass-length/time^2, so f=ma!)

Unit systems

           SI (MKS)           MD                     KCAL-ANGSTROM
---------  --------------  ------------------------  ------------------
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 (kg-m^2/s^2)  kJ/mol                    kcal/mol 
                             (Da-nm^2/ps^2)            (418.4 Da-A^2/ps^2)
force      N (kg-m/s^2)    kJ/(mol-nm) = TN/mol      kcal/(mol-A)
                             (Da-nm/ps^2) (T=10^12)    (418.4 Da-A/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.