### Log output: Start QMCFixedSampleLinearOptimize

Source: https://qmcpack.readthedocs.io/en/develop/_sources/lab_qmc_basics.rst.txt

Example of the log output marking the beginning of each linear optimization. The file root is O.q0.opt.s011 and append is set to no.

```text
=========================================================
  Start QMCFixedSampleLinearOptimize
  File Root O.q0.opt.s011 append = no
=========================================================
```

--------------------------------

### Install QMCPACK plugin for Quantum Package (QP2)

Source: https://qmcpack.readthedocs.io/en/develop/sCI.html

This script demonstrates the installation process for QP2 with the QMCPACK plugin, including environment configuration and compilation.

```bash
CC=gcc
CXX=g++
F90=gfortran
F95=gfortran
F77=gfortran
git clone https://github.com/QuantumPackage/qp2.git
cd qp2
#git checkout v2.2.2 # Example of using a specific released version
#git checkout dev-pbc # Periodic boundary condition development version
./configure -i all
./configure -c config/gfortran.cfg
source quantum_package.rc
ninja
cd plugins
git clone https://github.com/QuantumPackage/qmcpack.git
cd ../
qp_plugins install qmcpack
ninja
```

--------------------------------

### Install Quantum ESPRESSO serial with QMCPACK

Source: https://qmcpack.readthedocs.io/en/develop/installation.html

Installs Quantum ESPRESSO with QMCPACK in serial mode (no MPI) and without scalapack. The command is non-intuitive for Spack newcomers.

```bash
your-laptop> spack install quantum-espresso+qmcpack~patch~mpi~scalapack@6.7%gcc hdf5=serial

```

--------------------------------

### Configuring and Building with Release Type

Source: https://qmcpack.readthedocs.io/en/develop/installation.html

Example of configuring the build with a specific build type and executing the build.

```bash
cd build
cmake -D CMAKE_BUILD_TYPE=Release ..
make -j 8
```

--------------------------------

### Particleset elements for ions and electrons specifying electron start positions

Source: https://qmcpack.readthedocs.io/en/develop/_sources/simulationcell.rst.txt

Example demonstrating explicit specification of electron and ion positions using the particleset element.

```xml
<particleset name="e">
  <group name="u" size="4">
    <parameter name="charge">-1</parameter>
    <attrib name="position" datatype="posArray">
  2.9151687332e-01 -6.5123272502e-01 -1.2188463918e-01
  5.8423636048e-01  4.2730406357e-01 -4.5964306231e-03
  3.5228575807e-01 -3.5027014639e-01  5.2644808295e-01
     -5.1686250912e-01 -1.6648002292e+00  6.5837023441e-01
    </attrib>
  </group>
  <group name="d" size="4">
    <parameter name="charge">-1</parameter>
    <attrib name="position" datatype="posArray">
  3.1443445436e-01  6.5068682609e-01 -4.0983449009e-02
     -3.8686061749e-01 -9.3744432997e-02 -6.0456005388e-01
  2.4978241724e-02 -3.2862514649e-02 -7.2266047173e-01
     -4.0352404772e-01  1.1927734805e+00  5.5610824921e-01
    </attrib>
  </group>
</particleset>
<particleset name="ion0" size="3">
  <group name="O">
    <parameter name="charge">6</parameter>
    <parameter name="valence">4</parameter>
    <parameter name="atomicnumber">8</parameter>
  </group>
  <group name="H">
    <parameter name="charge">1</parameter>
    <parameter name="valence">1</parameter>
    <parameter name="atomicnumber">1</parameter>
  </group>
  <attrib name="position" datatype="posArray">
    0.0000000000e+00  0.0000000000e+00  0.0000000000e+00
    0.0000000000e+00 -1.4308249289e+00  1.1078707576e+00
    0.0000000000e+00  1.4308249289e+00  1.1078707576e+00
  </attrib>
  <attrib name="ionid" datatype="stringArray">
    O H H
  </attrib>
</particleset>
```

--------------------------------

### Particleset elements for ions and electrons randomizing electron start positions

Source: https://qmcpack.readthedocs.io/en/develop/_sources/simulationcell.rst.txt

Example showing how to define ion and electron particlesets where electron positions are randomized based on the ion set.

```xml
<particleset name="i" size="2">
  <group name="Li">
    <parameter name="charge">3.000000</parameter>
    <parameter name="valence">3.000000</parameter>
    <parameter name="atomicnumber">3.000000</parameter>
  </group>
  <group name="H">
    <parameter name="charge">1.000000</parameter>
    <parameter name="valence">1.000000</parameter>
    <parameter name="atomicnumber">1.000000</parameter>
  </group>
  <attrib name="position" datatype="posArray" condition="1">
  0.0   0.0   0.0
  0.5   0.5   0.5
  </attrib>
  <attrib name="ionid" datatype="stringArray">
     Li H
  </attrib>
</particleset>
<particleset name="e" random="yes" randomsrc="i">
  <group name="u" size="2">
    <parameter name="charge">-1</parameter>
  </group>
  <group name="d" size="2">
    <parameter name="charge">-1</parameter>
  </group>
</particleset>
```

--------------------------------

### Install dependencies and build QMCPACK on Ubuntu

Source: https://qmcpack.readthedocs.io/en/develop/_sources/installation.rst.txt

Installs required developer tools, libraries, and Python analysis packages via apt-get, then configures and builds the project.

```bash
sudo apt-get install cmake g++ openmpi-bin libopenmpi-dev libboost-dev
sudo apt-get install libopenblas-openmp-dev libhdf5-dev libxml2-dev libfftw3-dev
# For qmca and other python-based analysis tools tools:
sudo apt-get install python3-numpy python3-scipy python3-h5py python3-matplotlib
cd build
cmake -DCMAKE_C_COMPILER=mpicc -DCMAKE_CXX_COMPILER=mpiCC ..
make -j 8 # Adjust to available core count
ls -l bin/qmcpack
```

--------------------------------

### Example QMCPACK input file produced by convert4qmc

Source: https://qmcpack.readthedocs.io/en/develop/_sources/additional_tools.rst.txt

This is a sample QMCPACK input file generated by convert4qmc. It is recommended to start with only the initial VMC block and adjust parameters based on the measured energies, variance, and statistics.

```xml
<?xml version="1.0"?>
<simulation>
  <!--

Example QMCPACK input file produced by convert4qmc

It is recommended to start with only the initial VMC block and adjust
parameters based on the measured energies, variance, and statistics.

```

--------------------------------

### Define physical system in Nexus example.py

Source: https://qmcpack.readthedocs.io/en/develop/_sources/lab_qmc_basics.rst.txt

Sets up the physical system for a QMCPACK calculation using Nexus. Defines the project name and the pseudopotential files for PWSCF and QMCPACK. This is the minimal information needed to generate input files for an 8-atom cubic cell of diamond.

```python
# details of your physical system (diamond conventional cell below)
my_project_name = 'diamond_vmc'   # directory to perform runs
my_dft_pps      = ['C.BFD.upf']   # pwscf pseudopotentials
my_qmc_pps      = ['C.BFD.xml']   # qmcpack pseudopotentials
```

--------------------------------

### Assemble O.q0.opt.in.xml with includes and pseudo

Source: https://qmcpack.readthedocs.io/en/develop/_sources/lab_qmc_basics.rst.txt

Assemble the main QMCPACK input file O.q0.opt.in.xml by including the particle, wavefunction, and pseudopotential files. Comments are denoted by <!-- ... -->.

```xml
...
<!-- include simulationcell and particle information from pw2qmcpqack -->
<include href="O.q0.ptcl.xml"/>
...
<!-- include wavefunction information from pw2qmcpqack -->
<include href="O.q0.wfs.xml"/>
...
<!-- O pseudopotential read from "O.BFD.xml" -->
<pseudo elementType="O" href="O.BFD.xml"/>
...
```

--------------------------------

### QMCPACK XML input for charged cell determinants

Source: https://qmcpack.readthedocs.io/en/develop/_sources/lab_excited.rst.txt

XML input for QMCPACK wavefunction setup. The example shows a particleset with a group of 36 electrons (mass 1.0, charge -1) and a determinantset with two determinants (up and down) each of size 36. Comments indicate changing the size to 35 for a charged cell calculation.

```xml
  <particleset name="e" random="yes">
    <group name="u" size="36" mass="1.0"> ##Change size to 35
      <parameter name="charge"              >    -1                    </parameter>
      <parameter name="mass"                >    1.0                   </parameter>
    </group>
  ...
  ...
  <determinantset>
    <slaterdeterminant>
      <determinant id="updet" group="u" sposet="spo_u" size="36"> ##Change size to 35
        <occupation mode="ground" spindataset="0"/>
      </determinant>
      <determinant id="downdet" group="d" sposet="spo_d" size="36">
        <occupation mode="ground" spindataset="1"/>
      </determinant>
    </slaterdeterminant>
  </determinantset>
```

--------------------------------

### Run pw2qmcpack.x with p2q.in

Source: https://qmcpack.readthedocs.io/en/develop/_sources/additional_tools.rst.txt

Run pw2qmcpack.x with the p2q.in input file, redirecting output to p2q.out. This converts PWSCF wavefunctions saved with the prefix 'bulk_silicon'.

```bash
mpirun -np 1 pw2qmcpack.x < p2q.in>& p2q.out
```

--------------------------------

### Install Homebrew on macOS

Source: https://qmcpack.readthedocs.io/en/develop/_sources/installation.rst.txt

Install Homebrew on macOS. This is the first step of the Homebrew-based QMCPACK installation recipe.

```bash
/usr/bin/ruby -e "$(curl -fsSL
  https://raw.githubusercontent.com/Homebrew/install/master/install)"
```

--------------------------------

### Install QMCPACK with regression tests using spack install --test=root

Source: https://qmcpack.readthedocs.io/en/develop/installation.html

Runs the QMCPACK regression tests as part of the installation by adding --test=root to the spack install command. Use this to verify the build while installing the same mixed+complex configuration with GCC 7.2.0 and Intel MKL.

```bash
your-laptop> spack install --test=root qmcpack+mixed+complex%gcc@7.2.0 ^intel-mkl

```

--------------------------------

### Quick build with OpenMPI

Source: https://qmcpack.readthedocs.io/en/develop/_sources/installation.rst.txt

Use this command sequence to build QMCPACK on a system using OpenMPI.

```bash
cd build
cmake -DCMAKE_C_COMPILER=mpicc -DCMAKE_CXX_COMPILER=mpicxx ..
make -j 8
```

--------------------------------

### Install SeeK-path with pip

Source: https://qmcpack.readthedocs.io/en/develop/lab_excited.html

Install the SeeK-path Python library using pip. The --user flag installs it for the current user only.

```bash
>pip install --user seekpath

```

--------------------------------

### Quick build with default compiler settings

Source: https://qmcpack.readthedocs.io/en/develop/_sources/installation.rst.txt

Use this command sequence to build QMCPACK without explicitly specifying compiler wrappers.

```bash
cd build
cmake ..
make -j 8
```

--------------------------------

### Verify Docker installation with docker run hello-world

Source: https://qmcpack.readthedocs.io/en/develop/_sources/running_docker.rst.txt

Verifies that the Docker engine is installed and running correctly. Run this after installing Docker; restart your system if necessary.

```bash
docker run hello-world
```

--------------------------------

### pw2qmcpack.x input file p2q.in

Source: https://qmcpack.readthedocs.io/en/develop/_sources/additional_tools.rst.txt

Sample pw2qmcpack.x input file p2q.in. It sets the prefix to 'bulk_silicon' and outdir to './'. write_psir is set to .false. to avoid writing the real-space wavefunction.

```fortran
&inputpp
  prefix     = 'bulk_silicon'
  outdir     = './'
  write_psir = .false.
/
```

--------------------------------

### Run QMCPACK on water molecule example

Source: https://qmcpack.readthedocs.io/en/develop/introduction.html

Commands to run a DMC calculation on the water molecule example. Optionally add the QMCPACK binary to PATH. The run generates output files listed in the example.

```bash
cd ../examples/molecules/H2O.
```

```bash
export PATH=$PATH:location-of-qmcpack/build/bin
```

```bash
../../../build/bin/qmcpack simple-H2O.xml
```

```bash
qmcpack simple-H2O.xml
```

--------------------------------

### Install and build QMCPACK on Ubuntu (apt-get)

Source: https://qmcpack.readthedocs.io/en/develop/installation.html

Install required packages and build QMCPACK on Ubuntu or other apt-get-based distributions. Uses generic BLAS; a vendor-optimized BLAS is usually faster. Adjust the make job count to your core count.

```bash
sudo apt-get install cmake g++ openmpi-bin libopenmpi-dev libboost-dev
sudo apt-get install libopenblas-openmp-dev libhdf5-dev libxml2-dev libfftw3-dev
# For qmca and other python-based analysis tools tools:
sudo apt-get install python3-numpy python3-scipy python3-h5py python3-matplotlib
cd build
cmake -DCMAKE_C_COMPILER=mpicc -DCMAKE_CXX_COMPILER=mpiCC ..
make -j 8 # Adjust to available core count
ls -l bin/qmcpack

```

--------------------------------

### Verify Docker Installation

Source: https://qmcpack.readthedocs.io/en/develop/running_docker.html

Run this command to verify Docker is properly installed. Restart the system if necessary.

```bash
docker run hello-world

```