www.nextnano.com/documentation/tools/nextnano3/input_syntax/keywords/buffer-solutions.html
Buffer solutions: To control pH values in electrolytes.
It is possible to overwrite the database entries of
$buffer-solutions by
this keyword and its specifiers in the input file. You can also define a
completely new buffer which is not contained in the database. If you overwrite a
buffer that is contained in the database, it is necessary that you include
all specifiers, including the ones that you do not want to overwrite. The
program then uses all the values given in the input file and ignores all
database entries.
!------------------------------------------------------!
$buffer-solutions
optional !
buffer-name
character
required !
number-of-ions
integer
required !
ion-valency
double_array required
!
ion-name-1
character
required !
ion-name-2
character
required !
ion-name-3
character
optional ! (only necessary for some buffers,
e.g. PBS)
ion-name-4
character
optional ! (only necessary for some buffers,
e.g. PBS)
pKa
double_array required
! pKa at 25° C ( = 298.15 K)
dpKa_dT
double_array required
! d pKa / d T
z_acid
double_array
required ! charge on the conjugate acid species
$end_buffer-solutions
optional !
!------------------------------------------------------!
Syntax
Example 1: MOPS
!------------------------------------------------!
$buffer-solutions
!
!
buffer-name = MOPS
! MOPS (C7H15NO4S) +
NaOH
number-of-ions = 2
!
ion-valency = -1d0 +1d0
! (C7H14NO4S)-
Na+
ion-name-1 =
Mops^-
! C7H15NO4S <==> (C7H14NO4S)-
+ H+
ion-name-2 = Na^+
!
pKa =
7.31d0
! pKa at 25° C ( = 298.15 K)
! (Note: This pKa is thermodynamic value. The working pKa'
is 7.20.)
dpKa_dT =
-0.011d0
! d pKa / d T
z_acid =
0d0
! charge on the conjugate acid species (0
= C7H15NO4S)
!
$end_buffer-solutions
!
!------------------------------------------------!
Example 2: PBS (phosphate buffer)
The phosphate buffer is special (and thus more complicated) because it
consists of three pKa values (and it thus has four different
ions).
!------------------------------------------------!
$buffer-solutions
!
!
buffer-name = PBS
! PBS (phosphate buffer)
number-of-ions = 4
!
ion-valency = -1d0 -2d0
-3d0 1d0 !
(H2PO4)-
(HPO4)2- (PO4)3-
Na+
ion-name-1 =
H2PO4^-
! NaH2PO4 <==> (H2PO4)-
+ Na+
ion-name-2 = HPO4^2-
! Na2HPO4 <==> (HPO4)2-
+ 2 Na+
ion-name-3 = PO4^3-
!
ion-name-4 = Na^+
!
pKa =
2.15d0 7.21d0
12.33d0 ! pKa,1 pKa,2
pKa,3 at 25° C ( = 298.15
K)
dpKa_dT =
0.0044d0 -0.0028d0 -0.026d0 ! d pKa
/ d T
z_acid =
0d0 -1d0
-2d0 ! charge on the conjugate acid
species (0 = H3PO4,
-1 = (H2PO4)-
, -2 = (HPO4)2- )
!
$end_buffer-solutions
!
!------------------------------------------------!
For the explanations of the specifiers, please have a look at the database
section of the keyword $buffer-solutions .
|