量化常用单位和换算因子

1. 原子单位

原子单位（a.u.）定义为：电子质量me = 电子电荷e = Bohr半径 a0 = 1
在该单位制中，Planck常数h = 2π，于是ħ = 1。真空介电常数1/(4πε0)=1。真空光速c=α-1=137.036，其中α为精细结构常数。

原子单位与国际单位的关系为：
1 a.u.（长度）= a0 = 4πε0ħ2/(mee2) = 0.5291772083×10-10 m = 0.5291772083 Å
1 a.u.（质量）= me = 9.109534×10-31 Kg，[另：1 a.m.u.（质量）= 1822 a.u.]
1 a.u.（电荷）= e =1.6021892×10-19 C
1 a.u.（能量）= 1 Hartree = mee4/((4πε0)2ħ2) = 27.2114 eV = 15.56893 mDyne/Å
1 a.u.（角动量）= ħ = 1.0545887×10-34 J·s
1 a.u.（力常数）= 15.56893 mDyn/Å，1 mDyn/Å = 1 N/cm
1 a.u.（时间）= 2.4189×10-17 s
1 a.u.（偶极矩）= 2.541746231 Debye = 8.478×10-30 C·m
1 a.u.（红外强度）= 974.880100 km/mol

更多基本物理常数和换算因子，见
https://physics.nist.gov/cuu/Constants/index.html

2. 能量换算因子

　
波数
频率
能量E
分子能量Em
温度T
　
cm-1
MHz
×10-18J
eV
Hartree
kJ/mol
kcal/mol
K
1 cm-112.997925×1041.986447×10-51.239842×10-44.556335×10-61.196266×10-22.85914×10-31.438769
1 MHz3.33564×10-516.626076×10-104.135669×10-91.519830×10-103.990313×10-79.53708×10-84.79922×10-5
1 aJ50341.11.509189×10916.2415060.2293710602.2137143.93257.24292×104
1 eV8065.5412.417988×1080.160217713.674931×10-296.485323.06051.16045×104
1 Hartree219474.631376.579684×1094.35974827.2113812625.500627.5103.15773×105
1 kJ/mol83.59352.506069×1061.660540×10-31.036427×10-23.808798×10-410.239006120.272
1 kcal/mol349.7551.048539×1076.947700×10-34.336411×10-21.593601×10-34.184001503.217
1 K0.6950392.08367×1041.380658×10-58.61738×10-53.16683×10-68.31451×10-31.98722×10-31

其它能量换算因子：

1 kcal/mol = 6.948×10-14 erg
1 eV = 1.602×10-12 erg
1 Hartree = 4.36×10-11 erg = 2 Rydberg
1 erg = 1.439×1013 kcal/mol = 6.2415×1011 eV = 2.2937×1010 Hartree = 5.034×1015 cm-1