XMVB Documentation

This is the documentation of XMVB including introduction to VB methods, how to install and run XMVB, how to prepare the input file and read the output file, and tutorials.

As one of the modern chemical bonding theories, valence bond theory can provide intuitive chemical pictures for molecular structural properties and chemical reaction mechanisms. XMVB is a quantum chemistry program based on classical valence bond theory for ab initio electronic-structure calculations by using non-orthogonal orbitals and it has implemented all the mainstream VB methods and functions. XMVB can be used for the nature of chemical bonding theory and has become the accurate multi-configuration quantum chemistry program. Besides, XMVB has been taken as the only VB software in several international VB theory seminars. XMVB is the most popular and influential software for ab initio valence bond calculations in the world.

Contents:

• 1. Manual
  • 1.1. Overview
    • 1.1.1. Methods
    • 1.1.2. Installation
    • 1.1.3. Running a job
    • 1.1.4. Utilities
  • 1.2. Input
    • 1.2.1. Global control ($CTRL)
    • 1.2.2. Required for BPREP($BFI)
    • 1.2.3. description ($STR)
    • 1.2.4. Fragments definition ($FRAG)
    • 1.2.5. Orbital description ($ORB)
    • 1.2.6. AIM Section($AIM)
    • 1.2.7. Initial guess description ($GUS)
    • 1.2.8. Required when SCF=n ($SCF)
    • 1.2.9. Geometry description ($GEO)
  • 1.3. Output
    • 1.3.1. Main XMVB output file (.xmo)
    • 1.3.2. File with optimized VB orbitals (.orb) and orbital guess (.gus)
    • 1.3.3. File with additional information (.xdat)
    • 1.3.4. One-electron density file (.den)
    • 1.3.5. File with basis functions information (.info)
    • 1.3.6. File with coefficients for the structures/determinants (.coeff)
  • 1.4. Theory and Methodologies
    • 1.4.1. Introduction to VB Theory
    • 1.4.2. The Evaluation of Hamiltonian and Overlap Matrices
    • 1.4.3. Orbital Optimization
    • 1.4.4. The VBSCF Methods
    • 1.4.5. Post-VBSCF Method
    • 1.4.6. Solvation VB Methods
• 2. Tutorial
  • 2.1. BDE and RE of F₂
    • 2.1.1. Introduction
    • 2.1.2. Computations with 3 Structures at Stationary Point
    • 2.1.3. Computations with 3 Structures at Dissociation Limit
    • 2.1.4. Computations with Covalent Structure at Stationary Point
  • 2.2. Resonance in C₆H₆
    • 2.2.1. Introduction
    • 2.2.2. Computations with 5 Covalent Structures
    • 2.2.3. Computations with 2 Kekulé Structures
    • 2.2.4. Computations with 1 Kekulé Structure
  • 2.3. Menshutkin Reaction NH₃ + CH₃Cl \(\rightarrow\) [NH₃CH₃]⁺ + Cl^-
    • 2.3.1. Chemical question to be addressed
    • 2.3.2. Active/inactive electrons and orbitals
    • 2.3.3. Fragmentation and important VB structures
    • 2.3.4. Basis set and its subsets based on orbital symmetry
    • 2.3.5. Structures
    • 2.3.6. Input File
    • 2.3.7. Computational Results
  • 2.4. Potential Energy Surface of LiF (Optional)
    • 2.4.1. Introduction
    • 2.4.2. Computations near equilibrium
    • 2.4.3. Computations for Other distances
• 3. Citation