Q-Chem 是分子的結構、 活性，準確地預測綜合 ab 從頭算量子化學包和振動、 電子和核磁共振光譜。新的發行版本的 Q-Chem 4.0 表示方法論的先進最高性能的 DFT/高頻計算從高級別職位 HF 關聯方法： 色散更正和雙雜交 DFT 泛函 ； 離散傅立葉轉換、 高頻和耦合簇計算 ； 更快演算法 結構和振動激發態與泛函理論 ； 方法映射複雜的勢能表面 ； 高效價空間模型的強的相關性 ； 更多的選擇，激發的態、 溶劑和電荷轉移 ； 有效片段潛在和品質管制/毫米大系統 ； 共用記憶體 multicores 和 GPU 的實現。

　

Q-Chem is a comprehensive ab initio quantum chemistry package for accurate predictions of molecular structures, reactivities, and vibrational, electronic and NMR spectra. The new release of Q-Chem 4.0 represents the state-of-the-art of methodology from the highest performance DFT/HF calculations to high level post-HF correlation methods:

Dispersion-corrected and double hybrid DFT functionals;
Faster algorithms for DFT, HF and coupled-cluster calculations;
Structures and vibrations of excited states with TD-DFT;
Methods for mapping complicated potential energy surfaces;
Efficient valence space models for strong correlation;
More choices for excited states, solvation and charge-transfer;
Effective Fragment Potential and QM/MM for large systems;
Shared-memory for multicores and implementations for GPU's.
　

Property Analysis
Automated Geometry and Transition Structure Optimization
● Uses Dr. Jon Baker's OPTIMIZE package
     ○ Utilizes redundant internal coordinates to ensure rapid convergence
         even without an initial force constant matrix
● Geometry Optimization with General Constraints
     ○ Can impose bond angle, dihedral angle (torsion) or out-of-plane

         bend constraints Freezes atoms in Cartesian coordinates
     ○ Desired constraints do not need to be imposed in starting structure
● Optimizes in Cartesian, Z-Matrix or delocalized internal coordinates
● Eigenvector Following (EF) algorithm for minima and transition states ● GDIIS algorithm for minima
     ○ Greatly speeds up convergence to an equilibrium geometry
● Intrinsic Reaction Coordinates (IRC) following
     ○ Connect equilibrium geometries and transistion states along

         reaction paths.
     ○ Ab initio dynamics with extrapolated z-vector techniques for MP2

        and/or dual-basis methods
     ○ Improved robustness with Version 4.0
● Freezing and Growing String Methods for efficient automatic reaction path finding