The Nexus User Guide

Table of Contents

• Using this Guide
• Overview of Nexus
  • What Nexus is
  • What Nexus can do
  • How Nexus is used
• Nexus Installation
  • Setting environment variables
  • Installing Python dependencies
  • Testing your Nexus installation
• Nexus User Scripts
  • Nexus imports
  • Nexus settings: global state and user-specific information
  • Physical system specification
  • Workflow specification
  • Workflow execution
  • Limiting the number of submitted jobs
  • Data analysis
• Complete Examples
  • Example 1: Bulk Diamond VMC
  • Example 2: Graphene Sheet DMC
  • Example 3: C 20 Molecule DMC
  • Example 4 Automated oxygen dimer binding curve
  • Example 5: Bulk Diamond Excited States VMC
• Recommended Reading
  • Helpful Links for Installing Python Modules
  • Brushing up on Python
  • Quantum Monte Carlo: Theory and Practice
• Basic Python Constructs
  • Intrinsic types: int, float, str
  • Container types: tuple, list, array, dict, obj
  • Conditional Statements: if/elif/else
  • Iteration: for
  • Functions: def, argument syntax
• QMC Practice in a Nutshell
  • VMC and DMC in the abstract
  • From expectation values to random walks
  • Quality orbitals: planewaves, cutoffs, splines, and meshes
  • Quality Jastrows: less variance = more efficient
  • Finite size effects: k-points, supercells, and corrections
  • Imaginary time discretization: the DMC timestep
  • Population control bias: safety in numbers
  • The fixed node/phase approximation: varying the nodes/phase
  • Pseudopotentials: theoretical dissonance, the locality approximation, and T-moves
  • Other approximations: what else is missing?