# Quantum-mechanical simulation of the electronic structure in solids

## Instructions: Spring 2006

The way the labs are assessed is by the students giving a 10-12 minute presentation (10-12 slides), followed by questions. This should take place on the afternoon of Friday, 24th February.

Questions related to this computational experiment can be directed to Prof. Nicholas Harrison and Dr Giuseppe Mallia.

## Introduction

The properties of solids depend on the electronic structure, which is related to the nature of the interaction between atoms. In this laboratory you will use a quantum-mechanical program to calculate the electronic structure of an ionic, a covalent, a molecular and a metallic crystal.

## The Software: RedHat Linux, DLVisualize and CRYSTAL

Linux provides an excellent environment for numerical simulations so the first step is to reboot your computer into RedHat Linux.

The environment is not hugely dissimilar to that provided by Microsoft Windows. You will find a web browser (Mozilla) on the tool bar and under the Start Menu you will find some office tools (Writer, Math etc.) which are similar to those in Microsoft Office (Word, Excel etc.) and you may find them useful in plotting your data and writing your report.

DLVisualize is a general purpose graphical user interface for modelling. It will give you relatively easy access to a number of quantum mechanical and empirical simulation codes. In this case the interface to the code CRYSTAL.

The CRYSTAL program computes the ground state energy, electronic wave function and properties of periodic systems within Hartree Fock, density functional or various hybrid approximations, will be used.

There are web sites devoted to both DLV and CRYSTAL where you can find some additional information.

Further information about DLV

Further information about CRYSTAL

Before starting the exercises it is recommended to have a look the CRYSTAL input and output structure.
A quick tour of CRYSTAL input and output

Exercises:

1. An ionic crystal: MgO
MgO geometry input
MgO_geometry output
Run a MgO wavefunction calculation
Run a MgO properties calculation: 3D Charge Density
Run a MgO properties calculation: Charge Density Slide
Run a MgO properties calculation: Band Structure
Run a MgO properties calculation: Density of States
Run a MgO properties calculation: Band Structure + Density of States
Optimise the MgO structure
Calculate the MgO bulk modulus

2. A covalent crystal: Si (Si.inp)
Run a wavefunction calculation
Run a properties calculation: 3D Charge Density
Run a properties calculation: Charge Density Slide
Run a properties calculation: Band Structure
Run a properties calculation: Density of States
Run a properties calculation: Band Structure + Density of States

3. A molecular crystal: Urea - CO(NH2)2   (Urea.inp)
Urea geometry input
Run a wavefunction calculation
Run a properties calculation: 3D Charge Density
Run a properties calculation: Charge Density Slide
Run a properties calculation: Band Structure
Run a properties calculation: Density of States
Run a properties calculation: Band Structure + Density of States

4. A metallic crystal: Be (Be.inp)
Run a wavefunction calculation
Run a properties calculation: 3D Charge Density
Run a properties calculation: Charge Density Slide
Run a properties calculation: Band Structure
Run a properties calculation: Density of States
Run a properties calculation: Band Structure + Density of States