Micromeritics ASAP 2460 - Sphere Pore Geometry (Cheng;Yang

Appendix C ASAP 2460 Operator’s Manual
C-28 246-42800-01 - Aug 2013
P = equilibrium pressure
Po = saturation pressure
R = gas constant (8.31441 × 10
7
erg/mol K)
r
p
= radius of the cylindrical pore,
T = analysis bath temperature (K), from an entered or calculated value on the Po
and Temperature Options window
Sphere Pore Geometry (Cheng/Yang)
When you use the Cheng/Yang
11
method, the following equation is solved for each value of P. The
value of L is determined when the solved-for relative pressure is within 0.1% of the collected absolute
pressure.
where
10
32
= the number of cm
4
that are equal to Å
4
*
12
=, where 
*
22
=, where
d
0
=
where:
D
A
= molecular diameter (Å) from the Horvath-Kawazoe Physical Properties
window
D
S
= diameter of sample atom (Å) from the Horvath-Kawazoe Physical
Properties window
L = pore width (nucleus to nucleus) (Å)
N
1
=4 L
2
N
S
, where N
S
= number of sample atoms/cm
2
at monolayer
N
2
= 4 (L - d
0
)
2
N
A
, where N
S
= number of gas molecules/cm
2
P = equilibrium pressure
Po = saturation pressure
R = gas constant (8.31441 × 10
7
erg/mol K)
T = analysis bath temperature (K), from an entered or calculated value on the Po
and Temperature Options window
L
2
---
P
Po
-------


ln
6N
1

*
12
N
2

*
22
+ L
3
10
32

RTL d
0
–
3
------------------------------------------------------------------
d
0
L
----


6
T
1
12
------
T
2
8
-----
+


–
d
0
L
----


12
T
3
90
------
T
4
80
------
+


+
=
Å
S
4d
S
6
-------------
Å
S
6 mc
2

S

A

S

S
------

A

A
-------
+
--------------------------------
=
A
A
4D
A
6
---------------
Å
A
3 mc
2

A

A

2
-------------------------------------------
=
D
A
D
s
+
2
--------------------