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staventchoke

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[求助] 聚合物晶胞优化 已有1人参与

本人构建聚合物晶胞后进行几何优化处理,收敛曲线老是出现下图情况,请问MS高手这是怎么回事?

聚合物晶胞优化
1 Convergence.jpg
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【答案】应助回帖

感谢参与,应助指数 +1
Common reasons for minimization to fail

Forcefield typing error. Discover needs the forcefield type of each atom in the structure in order to determine which forcefield parameters to use. In some cases forcefield typing may fail. If this happens, you will not be able to successfully run a Discover job. See If typing fails for more information.
Charging failure. Discover needs a structure to be charged to be able to calculate the electrostatic energy. In some cases charging may fail or warnings be reported. In this case, a Discover job will be allowed to run, but any results obtained should be checked. See If charging fails for more information.
Discover job failure. See If a remote job fails for more information.
The cell multipole non-bond summation method is not supported for periodic systems in parallel. Switching to another summation method, such as charge groups or running on a single core will allow the job to run. See Selecting a summation method for more information.
Forcefield cross term failure.

Some forcefields such as COMPASS have additional valence terms called cross terms. These terms are required, for instance, to accurately reproduce experimental vibrational frequencies. However, if a structure is significantly distorted these terms can become large in magnitude and cause the optimizer to become trapped in a local minimum that is an artifact of these cross terms. If the output indicates that the cross terms are large and the final structure is not chemically reasonable, it is likely that a cross term failure has occurred. In this case pre-optimize the structure using the BTCL "forcefield scale cross = 0.0" command. (To do this you need to use the Files facility: set the required minimizer options on the minimizer dialog, save the input files from the Files dialog, edit the .inp file to add the "forcefield scale cross = 0.0" command and then run the job from the Files dialog). In most cases this will remove any unrealistic geometries. Finally optimize the structure obtained against the required forcefield.
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2楼2014-04-15 18:29:18
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