Ionocovalency correlates Mössbauer parameters d and Δ *

 Yonghe Zhang
 American Huilin Institute

 

As the IC, n*(Iav/R)½rc-1, is defined as ionocovalent density of the effective nuclear charges at covalent boundary, it strongly related with the Mössbauer parameters d and Δ. [40,41]. The value of the isomer shift,d, depends particularly on the density of s electrons at the nucleus. Therefore, in iron-57 an increase in electron density causes a negative isomer shift; since d electrons tend to shield the nucleus slightly from the s electrons the value of d falls as the number of d electrons in the iron atom falls. Mean values of d [42], Z* and IC for some oxidation states of iron are shown in Table.4.2: 

 

Table 4. 2  IC, Z* and d for iron-57  

Iron-57

FeI

FeII

FeIII

FeIV

FeV

d /mm s-1

2.3

1.5

0.7

0.2

-0.6

Z*= n*(Iav/R)½

2.624

3.245

3.997

4.896

5.684

IC=n*(Iav/R)½rc-1

2.253

2.786

3.431

4.203

4.879

 

[*] Zhang, Y. Ionocovalency and Applications 1. Ionocovalency Model and Orbital Hybrid Scales. Int. J.    

    Mol. Sci. 2010, 11, 4381-4406

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