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【求助】ReaxFF 力場參數(shù)化問題請教
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以下是引自Simulations on the Thermal Decomposition of a Poly(dimethylsiloxane) Polymer Using the ReaxFF Reactive Force Field,J. AM. CHEM. SOC. 2005, 127, 7192-7202的一個片段,是關(guān)于ReaxFF力場參數(shù)化的說明,不知道具體是怎么執(zhí)行的,希望有人可以一起探討下。 The force field was constructed by adding quantum chemical (QC) data for systems relevant to PDMS chemistry to the ReaxFF training set for Si/SiO materials. QC data for nonperiodic systems was obtained from DFT calculations performed using Jaguar (version 5.5) using the B3LYP functional and Pople’s 6-311G**++ basis set.22 The Mulliken charges were obtain using Pople’s 6-31G** basis set. To obtain the equation of state for disiloxane diol (HOMe2Si)2O crystal, DFT calculations were performed with the plane-wave code CASTEP (version 3.8) module in Cerius2. The generalized gradient approximation (GGA) proposed by Perdew, Burke, and Ernzerhof was used for the exchange-correlation energy, and ultrasoft pseudopotentials were used to replace the core electrons. We used the Perdew-Wang implementation of GGA with a kinetic energy cutoff of 380 eV. The Monkhorst-Pack scheme was used to generate the k-space grid with a 0.1 Å-1 spacing 請問以上這些具體是怎么操作的? 是不是可以理解成 1)、非周期性體系的QC數(shù)據(jù)用 DFT的 B3LYP/6-311G**++ 模型進(jìn)行計算;2)、Mulliken電荷從6-31G**基組的頻率計算獲得 3)、HOMe2Si的狀態(tài)方程用Cerius中的CASTEP模塊的Plane-wave方法獲得;4)、使用PBE-GGA計算關(guān)聯(lián)-交換能,超軟贗勢代替核電子;5)PW-GGA計算中,動能截斷取380eV;6)使用Monkhorst-Pack方案產(chǎn)生k-space格點,空間間隔為0.1埃 ? |
» 搶金幣啦!回帖就可以得到:
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你這里提到的細(xì)節(jié), 都是量化計算的, 嚴(yán)格意義上講和ReaxFF力場參數(shù)化的具體細(xì)節(jié)步驟沒啥關(guān)系.很明顯ReaxFF的參數(shù)都是在量化數(shù)據(jù)的基礎(chǔ)上fit得到的. 目前, 才訓(xùn)練參數(shù)的時候, 可以有這樣的幾類信息可以使用: Frequency, charge, heat_of_formation, geometry, cell parameter, energy_difference 這其中energy_difference使用得最多. 如果你用量化計算了反應(yīng)物, 反應(yīng)產(chǎn)物, 那么你就可以得到energy_difference.這樣一來, 對于訓(xùn)練參數(shù)的數(shù)據(jù)庫而言, 就又增加了一個target. 先說到這里, 滿意了嗎? |
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