DOC.
329
DECEMBER
1911 239
329.
From Fritz Haber
Dahlem
(Berlin), Königin
Luisestr.
14
19
December
1911
To
Prof. Dr.
Einstein,
Chair of Theoretical
Physics
at
the German
University, Prague
Highly
esteemed
Colleague:
It
is not
due
to
ungratefulness
but
to
ambition that
I
have not
written
to
you
earlier,
for
you
said
so
many
kind
things
in
your
letter[1]
that
I
felt
obliged
to
make
an
effort
to
justify
them.
You
will
read the
middling
result of
those efforts in
the
next
issue
of
the
Verhandlungen
der deutschen
physikalischen
Gesellschaft.[2]
The main
points
are
briefly
the
following:
A Coulomb
force
is
to be
introduced
in
the
equation
of
state
for solids.
The
value
for
the electrostatic
charge
of
the individual
electron
can
be
correctly
calculated
from the
compressibility
and the
atomic volume if
one assumes
that
this
Coulomb
force
opposes
the
compression.
The
solid
body
is
an
electronic
lattice in whose
meshes
the
positively
charged
particles
are
suspended.
The linear
oscillations of the
electrons
in this
lattice,
decomposed
in
two
cycles
of half
amplitude, produce
diamagnetism
in
the
presence
of
an
influence from
an
external
magnetic
field. With this
model,
one
obtains
exactly
the
right
order of
magnitude
and almost
the
right
magnitude
if
one
derives
the
susceptibility
from the
assumption
that
the maximum
amplitude is comparable to
the distance between
the
centers
of
two
atoms.
As in all of
these
arguments,
it
is
essential
for
the ratio of
the
maximum
amplitude
to
the
atomic
diameter
to
be
a
universal
quantity.
With
the
help
of the
same
model
one can
also
calculate the
paramagnetic
saturation from
the
frequency
of
the selective
photoelectric
ion
with
tolerable
accuracy.
This
picture
of the
electric solid
body
connects the
root
law with
your compressibility
law
and Lindemann's
formulas[3]
in
a
unified
way.
Apart
from
a
temperature-dependent
error,
the
quantity
hv
is
identical
with
the electrostatic
potential
of
the electron
in the
spatial
lattice of the
solid
multiplied
by
the
charge
of
the
electron.
Furthermore,
if the numerical values
are
correctly
chosen,
the
quantity
hv
agrees
to
within
3%
with
the heat of reaction
in all
of
the
examples
I calculated.
The
temperature
function
is
missing
in all
cases;
its
addition
would,
as
I believe,
completely
solve all difficulties.
From
a
theoretical
point
of
view,
I
regard
it
as a
great
lack
that
I do
not know
the
energy
equation
of
an
oscillator whose
frequency
depends
on
the
temperature.
This
is
characteristic of
the
majority
of natural
oscillators,
at
least of
the solid
ones.
It would be
of
the
greatest
value
to
know this
equation.
I
am
not
yet
finished with the
derivation of the thermal
effect
according
to
Richardson
from
the
same analyses,[4]
but
I
am
certain that
I will succeed in the
near