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798879443金蟲 (正式寫手)
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[求助]
優(yōu)化不收斂
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蟲友們好, 我對(duì)Co3(dpa)4(ncs)2進(jìn)行優(yōu)化,使用的是b3lyp方法,二重態(tài)和四重態(tài)都可以算出來,但是六重態(tài)總是收斂失敗,我后來降低了收斂精度,即使用conver=6,請(qǐng)問這樣處理可以保證其收斂嗎,還有與二、四重態(tài)還有可比性嗎,因?yàn)槲乙页瞿芰孔畹偷亩嘀囟,進(jìn)行加電場(chǎng)處理,請(qǐng)大神指教一下。 |

新蟲 (初入文壇)
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計(jì)算外加電場(chǎng)對(duì)Co3(dpa)4(NCS)2結(jié)構(gòu)影響時(shí),本來Co3(dpa)4(NCS)2從晶體數(shù)據(jù)庫取出來的結(jié)構(gòu)是對(duì)稱的,但NCS與Co3不在一條直線上,,我用bp86方法計(jì)算時(shí)加了nosymm關(guān)鍵詞,在加小電場(chǎng)是,Co3(dpa)4(NCS)2變成對(duì)稱的直線型了,隨著電場(chǎng)加大,Co3(dpa)4(NCS)2變成了非對(duì)稱性,請(qǐng)問是不是bp86方法得到的結(jié)果不好,隨后我又用b3lyp計(jì)算了,不過沒加nosymm關(guān)鍵詞,請(qǐng)問如果比較方法的可行性,這兩種處理有可比性,也就是nosymm關(guān)鍵詞對(duì)能量等有影響嗎,請(qǐng)大牛指點(diǎn),本人新人一枚。 兩者方法的關(guān)鍵詞為: #p opt nosymm bp86 genecp scf=maxcycles=500 #p opt b3lyp/genecp iop(2/15=1) 這里的注意一下關(guān)鍵字:IOp(2/15) Symmetry control. -1 Turns on symmetry; same as 0 for molecules but turns on assignment of space group operations for PBC. 0 Leave symmetry in whatever state it is presently in. 1 Unconditionally turn symmetry off. Note that symmetry is still called, and will determine the framework group. However, the molecule is not oriented. 2 Bring the molecule to a symmetry orientation, but then disable further use of symmetry. 3 Don't even call Symm. 4 Call Symm once with loose cutoffs, symmetrize the resulting coordinates then confirm symmetry with tight cutoffs. 5 Recover the previous symmetry operations from the RWF, and confirm that the new structure has the same symmetry. 6 Same as 5, but get symmetry info from the checkpoint. 00 Default (10). 10 Do re-orientation for PBC. 20 Suppress re-orientation for PBC. 100 Turn on symmetry operations for PBC. 如果你是想設(shè)置原子在同一直線上應(yīng)該使用冗余坐標(biāo)修改關(guān)鍵字。opt=modredundant 收斂指標(biāo)修改了當(dāng)然就和前面沒有對(duì)比性了。起碼只有在10的-6的級(jí)別上才有可靠的對(duì)比性?梢栽囅掠眯』M算,然后再用大基組算。如果你優(yōu)化發(fā)現(xiàn)能量變化只是在10的-6精度內(nèi),就可以降低收斂指標(biāo),等收斂后再用之前相同的指標(biāo)計(jì)算。 |

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