Hi,
I have a question. Is it possible to optimize charged unit cell, for example, if I want to investigate adsorption of charged species on neutral surface? If yes, where can I read about method, possible errors, etc?
Thank you in advance.
Optimization of charged unit cell
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Alenushka
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Optimization of charged unit cell
Last edited by Alenushka on Tue Jan 30, 2007 3:56 pm, edited 1 time in total.
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admin
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Optimization of charged unit cell
1) on charged systems in general, please have a look in the manual (chapter multipole corrections)
2) Actually, you MUST NOT set the number of electrons manually for a slab calculation. I.e., when you calculate the surface+adsorbate system, you are not allowed to select a specific charge state for the adsorbate by increasing the number of electrons manually. Specific charge state calculations make sense only in 3d systems and for cluster calculations.
The electrostatic energy of such a slab is however only conditionally convergent and in practice even infinite (BASIC, BASIC ELECTROSTATICS).
Only if the calcuations are done properly, i.e., if your slab is large enough and the lateral dimension (x,y) of your surface is large enough (test for the necessary 2D dimension, the total energy has to converge to the correct value with (1/(distance between the charged species) ) the energy should converge to the proper value, i.e. the adsorbed species should acquire the correct charge state (then, it is acquired automatically).
2) Actually, you MUST NOT set the number of electrons manually for a slab calculation. I.e., when you calculate the surface+adsorbate system, you are not allowed to select a specific charge state for the adsorbate by increasing the number of electrons manually. Specific charge state calculations make sense only in 3d systems and for cluster calculations.
The electrostatic energy of such a slab is however only conditionally convergent and in practice even infinite (BASIC, BASIC ELECTROSTATICS).
Only if the calcuations are done properly, i.e., if your slab is large enough and the lateral dimension (x,y) of your surface is large enough (test for the necessary 2D dimension, the total energy has to converge to the correct value with (1/(distance between the charged species) ) the energy should converge to the proper value, i.e. the adsorbed species should acquire the correct charge state (then, it is acquired automatically).
Last edited by admin on Thu Mar 08, 2007 8:12 am, edited 1 time in total.