Occupancy limits

cjb

Hi,

I'm struggling with limits on occupancy values. The problem can be simplified to the following example:

prm !tot_cu 1.1
prm !tot_zn 1.1
prm !tot_sn 0.8

site Cu1 occ Cu+1 cu_cu  0.2000  min 0 max 1
            occ Zn+2 zn_cu  = 1 - cu_cu;: 0.8000                                       
		                                                                                               
site Zn1 occ Cu+1 cu_zn  0.2000  min 0 max 1
            occ Zn+2 zn_zn  = 1 - cu_zn;: 0.8000
                                                                                                     
site Sn1 occ Cu+1 cu_sn  =tot_cu - cu_cu - cu_zn;: 0.7000
            occ Zn+2 zn_sn  =tot_zn - zn_cu - zn_zn;: -0.5000
            occ Sn+4 sn_sn  =tot_sn;

How do I limit the cu_cu and cu_zn occupancies such that zn_sn can't give a negative value, while still ensuring the total amount of each element is correct?

Any help much appreciated!

alancoelho

Hi cjb

You can write the occ for zn_sn as

occ Zn+2 zn_sn =tot_zn - (1 - cu_cu) - (1 - cu_zn);

or,
occ Zn+2 zn_sn =tot_zn + cu_cu + cu_zn - 2;

For positive values then we have:

(tot_zn + cu_cu + cu_zn - 2) >= 0
or,
cu_cu >= (2 - tot_zn - cu_zn)

Thus use min on cu_cu as follows:

site Cu1 occ Cu+1 cu_cu 0.2000 min = 2 - tot_zn - cu_zn; max 1