有名な理論的手法では,ベンゼンとアレンが非平面的であることが予測されている
Damian Moran1, Andrew C Simmonett, Franklin E Leach
1Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA.
Journal of the American Chemical Society
|July 20, 2006
まとめ
平面ベンゼンは,計算上の誤りのために,しばしば安定性として誤って予測されます. バランスの取れたベースセットは,ベンゼンおよび類似のpi-delocalized分子の非平面構造を正確に決定するために不可欠です.
科学分野:
- 計算化学はコンピュータ化学である.
- 量子化学は量子化学である.
- 分子モデリング
背景:
- 平面ベンゼンは,基本的な芳香分子である.
- 分子幾何学の正確な予測は化学において不可欠である.
- 以前の研究では,ベンゼンの予測された構造の不一致が示されました.
研究 の 目的:
- 平面ベンゼンを最小値として予測する計算上の失敗を調査する.
- ベンゼンおよび関連する分子における虚偽の架空の周波数の原因を特定する.
- アレン平面性の正確な予測に必要な計算条件を決定する.
主な方法:
- 様々な基本集合を持つ第2次モラープレッセット波動理論 (MP2) を利用した.
- 不安定性を示す想像上のモードを特定するために振動周波数を分析した.
- 計算上の予測におけるベースセット不完全性エラー (BSIE) の役割を調べました.
主要な成果:
- 不均衡なPople型ベースセットによるMP2計算は,平面ベンゼルを誤って予測する.
- 虚偽の架空の周波数は,平面外の歪み (椅子とボートの形状) に対応する.
- この失敗は,ピリジンやナフタレンなどの他のピ-デロカライズされたシステムでも観察されています.
結論:
- 不均衡なベースセット不完全性エラー (BSIE) は,平面ベンゼンの不正確な予測を原因としています.
- 相関波動関数法では,信頼性の高いアレーン幾何学予測のために,バランスのとれた,相関一貫したベースセットが必要です.
- この発見は,計算化学におけるベースセット選択の重要性を強調している.
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