Schmidt's rule

joelle

I'd like to know what the meaning of this expression : a crystal obeys schmidt's rule (in fact i don' t know what is the schmidt's rule)
If someone can help me i'll be grateful.
Thx

Related Atomic and Condensed Matter News on Phys.org

Gokul43201

Staff Emeritus
Gold Member
I think this is refering to Goldschmidt's Rule, which is an approximate rule of thumb telling you that substitutions that conserve oxidation state and ionic radius (approximately) introduce least strain in a crystal. This is something of an unwritten philosophy for a synthetic inorganic chemist or materials scientist. Pursuant to Goldschmidt's intuition was the excellent and extensive work done by Shannon and Prewitt on the influence of oxidation state on the ionic radius in a crystal. Shannon-Prewitt tables are a crystal-maker's Bible.

V. M. Goldschmidt was an early geochemist who contributed to the rise of crystallography and crystal chemistry in the mid-1920s.

Last edited:

PerennialII

Gold Member
.... and Schmidt's law is one classical yield rule used in single crystals,

$$\left|s^{(k)}_{i}\sigma_{ij}n^{(k)}_{j}\right| =\tau_{0}$$

where $s^{(k)}_{i}$ are the components of the slip direction in the kth slip system, $n^{(k)}_{j}$is the slip plane normal and $\sigma_{ij}$ the Cauchy stress tensor.

Gokul43201

Staff Emeritus
Gold Member
Now, I'm kinda sure that (Perennial's post) is what the OP wants. Ignore my previous post. Having had Goldschmidt sit in the back of my head for years made me think of his rule almost reflexively. Guess I should have Googled before posting to make sure there wasn't a Schmidt's Rule (I do not recall having seen it before).

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving