标题: What is the meaning of shoulder-like ? [打印本页] 作者Author: mekelleche 时间: 2020-5-24 08:58 标题: What is the meaning of shoulder-like ? Hi,
What's the meaning of the concept "shoulder-like" in IRC reaction path. 作者Author: sobereva 时间: 2020-5-24 09:44 (, 下载次数 Times of downloads: 21)
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Usually there is a factor potentially making energy increase 作者Author: mekelleche 时间: 2020-5-24 15:37
Does mean that there is an intermidiaite ? how we interpret a result like these ?作者Author: liyuanhe211 时间: 2020-5-24 20:01
No, otherwise the IRC will stop at the intermediate (unless there are problems with the IRC, e.g. step size too large, where there are examples of jumping through shallow intermediate).
There isn't any unified interpretation for such shape, you need to look at the trajectory, and maybe do proper wavefunction analysis for each point on the IRC. For example, sometimes it represents a concerted-asynchronous process, where the flat region is where the first step almost ends, and the second step just begin; sometimes it represents a possible steric repulsion or other penalties that need to be overcome during the conformation change (like a bond-forming event requires a simultaneous boat to chair conformation change, but the energy penalty of the conformation change is consistently smaller than that contributed by the bonding energy on any point of the IRC); and I have a rare case that two excited states cross around a minimum on one of the excited states, and during the IRC calculation, just before reaching the minimum, the electronic state changed, so that the energy could start to drop again following another PES.