Chemistry Reference
In-Depth Information
Table 1.1 Fundamental physical constants
Physical quantity
Value in SI units
10
19
C
Elementary charge
e
¼
1
:
602 176
10
31
kg
Electron mass
m
¼
9
:
109 382
10
34
Js
¼
:
Reduced Planck's constant
h
1
054 572
112 650 J
1
C
2
m
1
p
«
0
¼
:
Vacuum permittivity
4
1
10
8
ms
1
¼
:
Light velocity in vacuum
c
2
997 925
10
23
mol
1
Avogadro number
N
A
¼
6
:
022 142
10
23
JK
1
Boltzmann constant
k
¼
1
:
380 650
with the submultiples:
10
3
E
h
¼
mE
h
½
milliHartree
ð
1
:
76
Þ
10
6
E
h
¼ m
E
h
½
microHartree
ð
1
:
77
Þ
etc. The milliHartree is the characteristic unit for the energy of the
chemical bond, the microHartree is that for the energy of the Van der
Waals bond. The hydrogen bond has an intermediate energy, correspond-
ing to that of a weak chemical bond.
The basic au for dipole, quadrupole and octupole electric moments are
given as:
<
10
30
C
;
¼
:
Dipole moment
ea
0
8
478
m
10
18
esu
¼
2
:
542
cm
¼
2
:
542 D
10
40
C
ea
0
2
m
2
Quadrupole moment
;
¼
4
:
486
:
10
26
esu
cm
2
¼
1
:
345
¼
1
:
345 B
10
50
C
ea
0
3
m
3
Octupole moment
;
¼
2
:
374
10
35
esu
¼
7
:
117
cm
3
ð
1
:
78
Þ
In the expressions above, D is the Debye unit of electric dipole moment,
and B the Buckingham unit for the electric quadrupole moment.
At the end of a calculation in atomic units, as we shall usually do,
the actual SI values can be obtained by taking into account the SI
equivalents (1.74) and (1.78). As an example, we give below the
calculation of the SI equivalent of the Hartree unit to seven significant
figures:
