Question: how to calculate the energy of crystal

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    Crystal Energy
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Discussion Overview

The discussion revolves around calculating the energy of crystals, specifically focusing on tungsten oxide and its polymorphs (alpha, beta, and gamma). Participants explore theoretical approaches and practical implications related to energy differences among crystal phases.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant inquires about methods to calculate the energy of crystals, particularly the energy differences among various polymorphs of tungsten oxide.
  • Another participant suggests that density functional theory (DFT) is typically used to predict crystal structures from first principles, referencing a specific paper related to WO3.
  • A participant notes that the band gap values for a specific phase of WO3 vary significantly, questioning whether structural differences are the primary factor influencing energy levels.
  • One participant expresses confusion regarding the term "energy of a crystal," seeking clarification on whether it refers to bonding energy, electronic binding energy, or another concept.
  • The original poster acknowledges their lack of familiarity with the theoretical aspects and expresses a desire for simpler methods to characterize energy levels associated with different crystal phases.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the specific definition of "energy of a crystal" or the best methods for calculating it. Multiple viewpoints and uncertainties remain regarding the implications of different crystal phases and their energy levels.

Contextual Notes

The discussion highlights ambiguities in terminology and the need for clearer definitions related to crystal energy calculations. There is also a dependence on theoretical frameworks like density functional theory, which may not be accessible to all participants.

hymeme
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Dear all, I am recently dealing with crystals. There is one question which puzzles me a lot. How to calculate the energy of crystals? For example, tungsten oxide has severl polymorphs such as alpha, beta , and gamma. What is the energy difference among them. Hope you can help with this question. Thanks a lot!
 
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Usually, density functional theory is used to predict structures from first principles. An example for WO3 would be this paper.
 
Vagn said:
Usually, density functional theory is used to predict structures from first principles. An example for WO3 would be this paper.
thank you! From the paper, the value of the band gap various a lot for one specific phase. Does that mean such difference in structure is not the key factor which enfluences the energy much.(we synthesized WO3 experimentaly, but not familar with the theory. )
 
There is a lot of ambiguity in your question.

First of all, what exactly do you mean by "energy of a crystal"? It is hard to know if you want the bonding energy of a particular crystal configuration, the electronic binding energy, etc. In fact, you thank Vagn for giving you a paper that theoretically derived the band structure of a crystal. Is the electronic band structure what you actually meant by "energy of a crystal"?

So what exactly are you looking for here?

Zz.
 
ZapperZ, Thank you very much for the thoughtful reply. My question is not clear because I am not a physicist and not familiar with this area. This question occurred to me when we were synthesizing WO3 nanoparticles. At different temperature, the phase of the product is different. So I was wondering that different phase must have different energy level. I have hard time to find the right method to characterize such 'energy'. Band structure is good to know. But it will be best if there is another simple way.
 

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