add a unit for eV (#59)

Author: NoureldinYosri

tunits/core/cython/derived_unit_data.pyx

@@ -78,7 +78,8 @@ __SI_DERIVED_UNITS = [
     DerivedUnitData('lx', 'lux', 'lm/m^2', use_prefixes=True),
     DerivedUnitData('Bq', 'becquerel', 'Hz', use_prefixes=True),
     DerivedUnitData('l', 'liter', 'm^3', exp10=-3, use_prefixes=True),
-    DerivedUnitData('phi0', 'magnetic_flux_quantum', 'J*s/C', value=2.067833831170082e-15, use_prefixes=True)
+    DerivedUnitData('phi0', 'magnetic_flux_quantum', 'J*s/C', value=2.067833831170082e-15, use_prefixes=True),
+    DerivedUnitData('eV', 'electron_volt', 'N*m', value=1.602176634e-19, use_prefixes=False),
 ]
 
 __OTHER_UNITS = [

tunits/units.py

@@ -480,6 +480,7 @@
 e = core.default_unit_database.known_units['e']
 electron_mass = core.default_unit_database.known_units['electron_mass']
 elementary_charge = core.default_unit_database.known_units['elementary_charge']
+eV = core.default_unit_database.known_units['eV']
 eps0 = core.default_unit_database.known_units['eps0']
 exaampere = core.default_unit_database.known_units['exaampere']
 exabecquerel = core.default_unit_database.known_units['exabecquerel']
@@ -1703,6 +1704,7 @@
     "e",
     "electron_mass",
     "elementary_charge",
+    "eV",
     "eps0",
     "exaampere",
     "exabecquerel",

tunits/units_with_dimension.py

@@ -480,6 +480,7 @@
 e = core.Charge(core.default_unit_database.known_units['e'])
 electron_mass = core.Mass(core.default_unit_database.known_units['electron_mass'])
 elementary_charge = core.Charge(core.default_unit_database.known_units['elementary_charge'])
+eV = core.Energy(core.default_unit_database.known_units['eV'])
 eps0 = core.default_unit_database.known_units['eps0']
 exaampere = core.ElectricCurrent(core.default_unit_database.known_units['exaampere'])
 exabecquerel = core.Frequency(core.default_unit_database.known_units['exabecquerel'])
@@ -1705,6 +1706,7 @@
     "e",
     "electron_mass",
     "elementary_charge",
+    "eV",
     "eps0",
     "exaampere",
     "exabecquerel",