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zhengjifine

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[求助] castep 计算过度金属掺杂ZnO磁性问题！！

我在计算Cu 掺杂ZnO磁性的时候遇到一个奇怪的问题，在设置成反铁磁的时候，计算结果怎么会是铁磁的结果啊？哪位高手帮忙解答一下，下面附上图！
第一张图是模型，设置成反铁磁；
第二张图是计算的结果输出文件截图，可以看出上面的2*integrated spin density =2.000 这很显然是铁磁性的结果。
第三张图是布局分析里铜的自旋

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1楼2011-08-21 10:55:32

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zdsk

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【答案】应助回帖

★
zhengjifine(金币+3): 2011-08-21 12:49:39
zhengjifine(金币+1): 但是帮助文件中说：Uncheck the Fix occupancy checkbox and check the Optimize total spin checkbox. 2011-08-21 12:50:59
youzhizhe(金币+1): 谢谢交流。 2011-08-22 20:39:14

应该是设置SCF里的不要选6步后的优化选项。

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2楼2011-08-21 11:45:24

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zhengjifine

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谢谢回复，但是如果是这样的话，就和MS帮助文件里设置磁性计算的说明矛盾了。
Spin polarization
Magnetic systems can be studied by carrying out spin-polarized DFT calculations with CASTEP. This setting is recommended for transition metal oxides, certain inorganic surface studies, and metallic systems containing magnetic elements (Fe, Co, Mn, Ni).

Spin-polarized CASTEP calculations are normally carried out with a variable magnetic moment. This procedure, however, does not guarantee finding the lowest energy state. DFT solutions can converge to a variety of local minima, so that the metastable states are found. The most commonly obtained solutions correspond to high spin and low spin states. The state generated by CASTEP depends on the initial magnetic configuration, since the solution is likely to converge to the nearest local minimum rather than to the global minimum.

There are two ways of defining the initial magnetic configuration: either specify the total magnetic moment per unit cell, which gets uniformly distributed over the space, or provide detailed information on the absolute values and direction (up or down) of the spins for each atom in the unit cell. The former method can be used for relatively simple systems where only two solutions are expected (magnetic and non-magnetic). The latter method, which specifies the spin state of the atoms in the system, is more general and gives much more flexibility. It is possible to set up ferromagnetic, ferrimagnetic, or antiferromagnetic calculations to get different starting spin arrangements.

To set up a spin-polarized calculation with a uniformly distributed initial magnetic moment

Choose Modules | CASTEP | Calculation from the menu bar to display the CASTEP Calculation dialog.
Select the Setup tab.
Check the Spin polarized checkbox and uncheck the Use formal spin as initial checkbox.
Specify an Initial spin value.
To optimize the spin value, select the Electronic tab and click on the More... button to access the CASTEP Electronic Options dialog.
Select the SCF tab.
Uncheck the Fix occupancy checkbox and check the Optimize total spin checkbox.

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3楼2011-08-21 12:49:25

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