[交流] [讨论]Material Studio中构建合金结构或掺杂结构模型

Originally posted by hityanyan at 2008-5-29 21:53:
从网上搜了一些方法，结合自己的试验，总结如下,新人，请高手指点：
比如构建BexZn(1-x)O晶胞
方法1   
file->import->metal oxide->ZnO
选择图中所有Zn原子，在property 框中双击compositio ...

Mixture atoms
Atomic sites in a crystal can also be described in terms of a hybrid atom that consists of two or more element types. The relative concentrations can be set for any number of atoms, but the total concentration must not exceed 100%. The mixture atoms description is the most often used representation of solid solutions, metallic alloys, disordered minerals, etc.

Disorder and first principles calculations
There are a number of different approaches for dealing with disorder in first principles calculations:

Virtual crystal approximation (VCA): this offers technically the simplest approach, allowing calculations on disordered systems to be carried out at the same cost as calculations for ordered structures. VCA ignores any possible short range order and assumes that on each potentially disordered site there is a virtual atom which interpolates between the behavior of the actual components. This approach neglects such effects as local distortions around atoms and cannot be expected to reproduce the finer details of the disordered structures very accurately.

Using large ordered supercells followed by configurational averaging: this is a very expensive approach with limited applicability. For example, it is not possible to treat arbitrary and particularly small concentrations.

Coherent potential approximation (CPA): this method approximates a configurationally random alloy with an effective medium that is determined self-consistently from the condition of stationary scattering. The CPA technique is used extensively with model Hamiltonians with well-known scattering properties or in the context of multiple scattering methods of band structure calculation (KKR, LMTO). CPA is not well suited to total energy calculations or geometry optimization tasks.

"Computational alchemy": this method uses the perturbation theory to calculate the response to the difference between the true and VCA potentials. This approach is very demanding computationally, as are all linear response calculations.