NEB计算过渡态
2010-04-08 09:03:07| 分类： VASP|字号 订阅
首先下载code，script, 按照网站上的说明与VASP结合安装。
计算时事先用VASP优化出初始态和终了态。
用脚本nebmake，按照差值取出一系列中间结构，即IMAGES。
chmod a+x nebmake.pl
INCAR中设置SPRING=-5，以及IMAGES的数量（必须是核的整数倍）。
等整个计算收敛后，用vfin 以及 nebresult 处理得到势垒曲线。
官方网站： https://theory.cm.utexas.edu/vtsttools/
上面有关计算设置，以及脚本用法的信息很详细
The nudged elastic band (NEB) is a method for finding saddle points and minimum energy paths between known reactants and products. The method works by optimizing a number of intermediate images along the reaction path. Each image finds the lowest energy possible while maintaining equal spacing to neighboring images. This constrained optimization is done by adding spring forces along the band between images and by projecting out the component of the force due to the potential perpendicular to the band.
Difference from the implementation in VASP
There are a few improvements to the NEB method which are not yet included in the current version of vasp. A new tangent definition and a climbing image method combine to allow for the more accurate finding of saddle points using the NEB with fewer images than the original method. The setup and operation of this implementation can be identical to what is described in the vasp manual under the elastic band section. The new tangent is implemented by default, and the climbing image method can be turned by setting LCLIMB=.TRUE. in the INCAR file.
Climbing Image
The climbing image is a small modification to the NEB method in which the highest energy image is driven up to the saddle point. This image does not feel the spring forces along the band. Instead, the true force at this image along the tangent is inverted. In this way, the image tries to maximize it's energy along the band, and minimize in all other directions. When this image converges, it will be at the exact saddle point.
Because the highest image is moved to the saddle point and it does not feel the spring forces, the spacing of images on either side of this image will be different. It can be important to do some minimization with the regular NEB method before this flag is turned on, both to have a good estimate of the reaction co-ordinate around the saddle point, and so that the highest image is close to the saddle point. If the maximum image is initially very far from the saddle point, and the climbing image was used from the outset, the path would develop very different spacing on either side of the saddle point.
To use the climbing image, set LCLIMB=.True.
Standard Parameters