#!/usr/bin/env python
# coding: utf-8

# # Creating structures in pyiron

# This section gives a brief introduction about some of the tools available in pyiron to construct atomic structures. 

# For the sake of compatibility, our structure class is written to be compatible with the popular Atomistic Simulation Environment package ([ASE](https://wiki.fysik.dtu.dk/ase/)). This makes it possible to use routines from ASE to help set-up structures.
# 
# Furthermore, pyiron uses the [NGLview](http://nglviewer.org/nglview/latest/api.html) package to visualize the structures and trajectories interactively in 3D using NGLview-widgets.

# As preparation for the following discussion we import a few python libraries

# In[1]:


import numpy as np
get_ipython().run_line_magic('matplotlib', 'inline')
import matplotlib.pylab as plt


# and create a pyiron project named 'structures':

# In[2]:


from pyiron.project import Project
pr = Project(path='structures')


# ## Bulk crystals

# In this section we discuss various possibilities to create bulk crystal structures.

# ### Using `create_structure()`

# The simplest way to generate simple crystal structures is using the inbuilt `create_structure()` function specifying the element symbol, Bravais basis and the lattice constant(s)
# 
# Note: The output gives a cubic cell rather than the smallest non-orthogonal unit cell.

# In[3]:


structure = pr.create_structure('Al', 
                            bravais_basis='fcc', 
                            lattice_constant=4.05)


# To plot the structure interactively in 3D simply use:

# In[4]:


structure.plot3d()


# ### Using `create_ase_bulk()`
# 
# Another convenient way to set up structures is using the `create_ase_bulk()` function which is built on top of the ASE build package for [bulk crystals](https://wiki.fysik.dtu.dk/ase/ase/build/build.html#ase.build.bulk). This function returns an object which is of the pyiron structure object type.

# **Example:** fcc bulk aluminum in a cubic cell

# In[5]:


structure = pr.create_ase_bulk('Al', cubic=True)
structure.plot3d()


# **Example:** wurtzite GaN in a 3x3x3 repeated orthorhombic cell.
# 
# Note: 
# - In contrast to new_structure = structure.repeat() which creates a new object, set_repeat() modifies the existing structure object.
# - Setting `spacefill=False` in the `plot3d()` method changes the atomic structure style to "ball and stick".

# In[6]:


structure = pr.create_ase_bulk('AlN', 
                           crystalstructure='wurtzite', 
                           a=3.5, orthorhombic=True)
structure.set_repeat([3,3,3])
structure.plot3d(spacefill=False)


# ### Using the ASE spacegroup class

# In[7]:


from ase.spacegroup import crystal
from pyiron import ase_to_pyiron

a = 9.04
skutterudite = crystal(('Co', 'Sb'),
                       basis=[(0.25, 0.25, 0.25), (0.0, 0.335, 0.158)],
                       spacegroup=204,
                       cellpar=[a, a, a, 90, 90, 90])
skutterudite = ase_to_pyiron(skutterudite)


# In[8]:


skutterudite.plot3d()


# ## Accessing the properties of the structure object

# Using the bulk aluminum fcc example from before the structure object can be created by

# In[9]:


structure = pr.create_ase_bulk('Al', cubic=True)


# A summary of the information about the structure is given by using

# In[10]:


print(structure)


# The cell vectors of the structure object can be accessed and edited through

# In[11]:


structure.cell


# The positions of the atoms in the structure object can be accessed and edited through

# In[12]:


structure.positions


# ## Point defects

# ### Creating a single vacancy

# We start by setting up a 4x4x4 supercell

# In[13]:


structure = pr.create_ase_bulk('Al', cubic=True)
structure.set_repeat([4,4,4])


# To create the vacancy at position index "0" simply use:

# In[14]:


del structure[0]


# To plot the structure that now contains a vacancy run:

# In[15]:


structure.plot3d()


# ### Creating multiple vacancies

# In[16]:


# First create a 4x4x4 supercell
structure = pr.create_ase_bulk('Al', cubic=True)
structure.set_repeat([4,4,4])
print('Number of atoms in the repeat unit: ',structure.get_number_of_atoms())


# The `del` command works for passing a list of indices to the structure object. For example, a random set of n$_{\text{vac}}$ vacancies can be created by using

# In[17]:


# Generate a list of indices for the vacancies
n_vac = 24
vac_ind_lst = np.random.permutation(len(structure))[:n_vac]

# Remove atoms according to the "vac_ind_lst"
del structure[vac_ind_lst]


# In[18]:


# Visualize the structure
print('Number of atoms in the repeat unit: ',structure.get_number_of_atoms())
structure.plot3d()


# ### Random substitutial alloys

# In[19]:


# Create a 4x4x4 supercell
structure = pr.create_ase_bulk('Al', cubic=True)
structure.set_repeat([4,4,4])


# Substitutional atoms can be defined by changing the atomic species accessed through its position index.
# 
# Here, we set $n_{\text{sub}}$ magnesium substitutional atoms at random positions

# In[20]:


n_sub = 24
structure[np.random.permutation(len(structure))[:n_sub]] = 'Mg'


# In[21]:


# Visualize the structure and print some additional information about the structure
print('Number of atoms in the repeat unit: ',structure.get_number_of_atoms())
print('Chemical formula: ',structure.get_chemical_formula())
structure.plot3d()


# ## Explicit definition of the structure
# 
# You can also set-up structures through the explicit input of the cell parameters and positions

# In[22]:


cell = 10.0 * np.eye(3) # Specifying the cell dimensions
positions = [[0.25, 0.25, 0.25], [0.75, 0.75, 0.75]]
elements = ['O', 'O']

# Now use the Atoms class to create the instance.
O_dimer = pr.create_atoms(elements=elements, scaled_positions=positions, cell=cell)

O_dimer.plot3d()


# ## Surfaces (with ASE)
# 
# Some more commonly studied surfaces can also be defined with the `create_surface()` function based on the [ASE surface builder](https://wiki.fysik.dtu.dk/ase/ase/build/surface.html)

# In[23]:


fcc111 = pr.create_surface("Pt", 
                           surface_type="fcc111", 
                           size=(3, 4, 5), 
                           a=4.2, 
                           vacuum=20)


# In[24]:


fcc111.plot3d()


# ## Importing from cif/other file formats
# 
# Parsers from ASE can be used to import structures from other formats. In this example, we will download and import a Nepheline structure from the [Crystallography Open Database (COD)](http://www.crystallography.net/cod/index.php)

# In[25]:


# The COD structures can be accessed through their unique COD identifier
filename = '1008753.cif'
url = 'http://www.crystallography.net/cod/{}'.format(filename)


# In[26]:


# Download and save the structure file locally
import urllib
urllib.request.urlretrieve(url=url, filename='strucs.'+filename);


# In[27]:


# Using ase parsers to read the structure and then convert to a pyiron instance
import ase
from pyiron import ase_to_pyiron

structure = ase_to_pyiron(ase.io.read(filename='strucs.'+filename,
                                      format='cif'))


# In[28]:


structure.plot3d()


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