Hello I would like to simulate system containing montmorillonite where are also some Fe3+ atoms
(substitutions of Al3+). Here is for the illustration ideal chemical formula:
(Si4.0) (Al1.45Fe3+0.21Mg0.24Ti0.01) K0.07Na0.25Ca0.10 O10(OH)2
I build my "approximative" model using one existing MMT X-ray structure.
( http://www.crystallography.net/cod/9002779.html ).
I simply created the surface layer and several "Al" atoms substituted with "Fe".
Then I added the right number of ions (Na+, Ca2+, K+) and charged this my system using "Qeq" methodology (here is possible to download my final MMT system (*.xsd) http://www.uschovna.cz/en/zasilka/FR5R4YPBVFFNWYAL-YPR/ ) but I am not sure if this method "considers" "Fe" atoms here as Fe3+ as I need and not for example just as the Fe2+ because after charging procedure, charge of "Al" atoms is cca +1.2 but charge of "Fe" substitutive atoms only cca +0.7 which is similar to charge of "Mg" (Mg2+) atoms which is cca +0.75 .
So I am afraid that the Qeq methodology interpreted here my "Fe" atoms as the Fe2+ only.
This is indicated not only by very similar charge of "Fe" atoms with "Mg" (which should be here in Mg2+ form), low charge comparing to "Al" atoms which are here in Al3+ form but it is indicated also by values of FORMAL charges which I see after clicking on the given atom in properties explorer.
Default formal charges:
Al 3
Fe 2
Mg 2
I tried to change formal charge of "Fe" atoms to 3 and then to repeat Qeq calculation, but this did not changed the previous situation e.g. "Fe" atoms were again charged to cca +0.7 .
So I would like to know if is there some possibility to "tell" to the Qeq method something like "Please consider all the Fe atoms in the given structure as the Fe3+ and assign appropriate charge" or if simply in my case (simulation of MMT containing Fe atoms in Fe3+ state) is common to be satisfied with "Fe2+" state in model or even more simplified (but from the charge point of view
maybe better than the previous one) situation where Fe atoms which usually substitutes some relatively small part of Al atoms are simply omitted (replaced with Al).
Thank you very much in advance for any helpful information ! Best wishes, Marek
(substitutions of Al3+). Here is for the illustration ideal chemical formula:
(Si4.0) (Al1.45Fe3+0.21Mg0.24Ti0.01) K0.07Na0.25Ca0.10 O10(OH)2
I build my "approximative" model using one existing MMT X-ray structure.
( http://www.crystallography.net/cod/9002779.html ).
I simply created the surface layer and several "Al" atoms substituted with "Fe".
Then I added the right number of ions (Na+, Ca2+, K+) and charged this my system using "Qeq" methodology (here is possible to download my final MMT system (*.xsd) http://www.uschovna.cz/en/zasilka/FR5R4YPBVFFNWYAL-YPR/ ) but I am not sure if this method "considers" "Fe" atoms here as Fe3+ as I need and not for example just as the Fe2+ because after charging procedure, charge of "Al" atoms is cca +1.2 but charge of "Fe" substitutive atoms only cca +0.7 which is similar to charge of "Mg" (Mg2+) atoms which is cca +0.75 .
So I am afraid that the Qeq methodology interpreted here my "Fe" atoms as the Fe2+ only.
This is indicated not only by very similar charge of "Fe" atoms with "Mg" (which should be here in Mg2+ form), low charge comparing to "Al" atoms which are here in Al3+ form but it is indicated also by values of FORMAL charges which I see after clicking on the given atom in properties explorer.
Default formal charges:
Al 3
Fe 2
Mg 2
I tried to change formal charge of "Fe" atoms to 3 and then to repeat Qeq calculation, but this did not changed the previous situation e.g. "Fe" atoms were again charged to cca +0.7 .
So I would like to know if is there some possibility to "tell" to the Qeq method something like "Please consider all the Fe atoms in the given structure as the Fe3+ and assign appropriate charge" or if simply in my case (simulation of MMT containing Fe atoms in Fe3+ state) is common to be satisfied with "Fe2+" state in model or even more simplified (but from the charge point of view
maybe better than the previous one) situation where Fe atoms which usually substitutes some relatively small part of Al atoms are simply omitted (replaced with Al).
Thank you very much in advance for any helpful information ! Best wishes, Marek
