Quantum Chemistry
Throughout this course, we will use Jupyter notebooks to explore the material. Your first assignments will provide you with some basic background in Jupyter, Python, and Numpy. (I had been hoping to use Julia, which is arguably easier, but the online tools presently available at McMaster seem not to support Julia.)
In this course, we will primarily use the Python programming language. The best way to learn a programming language is to practice it on your own and learn through trial and error. Making mistakes helps you improve, so if at any point you get stuck, don’t get discouraged, seek help, and keep coding! There are many great resources online for learning about programming, so the course content for this topic is mostly based on external sources, especially LinkedIn Learning.
Programming is the process of writing a set of instructions (like a step-by-step recipe) that tells a computer how to perform a certain task. This recipe is written in a code called programming language. Similar to human languages, programming languages have syntax (the rule for writing instructions) and semantics (the meaning of the instructions). Also like human languages, there are lots of programming languages to choose from, each of these languages has its own history, features, and applications, but they all share the same fundamental ideas. You will learn more about programming languages by watching this 3-minute YouTube video here.
The most popular programming languages are either interpreted or compiled. For example, Python is an interpreted language. The Python interpreter reads a set of code instructions written in Python and translates it into a set of instructions for the computer to follow, and these instructions are then executed. This is analogous to the way a human language interpreter translates the spoken word from one language to another, on the fly. Compiled languages in compiled languages like C++ or Fortran, an entire computer program (or a large section thereof) is translated into instructions for the computer to follow, which is subsequently executed. This is analogous to the way a human translator might translate a book: the book is translated one chapter at a time, and perhaps content is rearranged to make it more idiomatic for the new language; then the book is read. Some other languages (e.g., Julia) are just-in-time translated, which is like translating a book chapter only after you are sure someone will read it, and potentially catering your translation to the particular person reading the book. Obviously compiled languages can be more efficient computationally, but they are also more complicated to use because the modules of the computer program must be translated from the human-readable computer language to machine-readable instructions(“compiled”), then combined together (“linked”), before they are finally executed. In this course we will use mainly Python, which is an interpreted language.
Computers always do exactly what they are told to do, so when you write a program, it is important to be clear, precise, and explicit about what you want the computer to do. It is therefore extremely important to learn the syntax and semantics of the language you use.
While computers always do exactly what you tell them to do, so in some sense they cannot do anything you could not do yourself. However, they allow you to perform those actions more efficiently. As Steve Jobs said, a computer is a bicycle for the mind. And thus learning to program a computer is like learning to ride a bicycle.
There are many programming languages out there, and each language has its unique advantages and disadvantages. Once you learn the basics of programming in one language, you can generally apply the same concepts to other languages. Python is one of the fastest-growing programming languages (Dropbox, Instagram, Netflix, and Google use Python extensively) and it is increasing popular in chemistry too. For more about the advantages of Python, watch the 2-minute video segment.
Compared to most other languages, Python is easier to read and write. It’s syntax is relatively simple, yet its flexibility—its ability to perform tasks from web development to scientific computing—is nearly unsurpassed. Importantly, there are a large number of plug-and-play Python libraries, which allow one to extend the basic features of the Python language with additional features. We will, for example, find the Numpy and Scipy libraries especially helpful.
To write and execute your code, you need to have access to the appropriate intepreters/compilers either through a web brower or locally on your computer. In this course, we will be using online Jupyter notebooks. Jupyter notebooks provides an interactive computing environment, originally focussed on Julia, Python, and R, though other languages are supported now.
Numpy is a Python library that provides methods for manipulating vectors and matrices in Python. For example, Numpy can be used to determine the eigenvalues and eigenvectors of a matrix, or to solve a system of linear equations. Numpy undergirds many of the most useful scientific software packages, and provides most of the key mathematical tools that are needed in this course.
In this course, we will use a JupyterHub that is provided free to most Canadian university students called syzygy.ca. Please
To learn more about Jupyter, programming concepts, Python programming, and Numpy, your first assignments are LinkedIn Learning courses. Before you get started, it’s helpful to log into LinkedIn Learning. (However, the links provided should automatically prompt you to log in if you are not already.) If you already have a LinkedIn account associated with a different e-mail, you can link your accounts. Upon completing each course, download your certificate of completion and upload it as your assignment. You can also add the certificate to your LinkedIn profile. You will have assignments to teach you how to
In addition, you can submit extra credit assignments.
If you would like to use Python and Jupyter locally, the easiest way to do this is probably by using the Anaconda distribution of Python, which simplifies many of the challenges a new programmer will encounter. For example, Anaconda’s package manager allows you to easily install different versions of Python and third-party Python packages for various operating systems, including:
You can then open the Anaconda Navigator and launch a Jupyter Notebook.
There are many free and paid resources available for deepening your knowledge of Python including videos, tutorials, courses, and books. The following are recommended. For tutorial-based courses, if you can somehow document your completion of the tutorial, then you can submit the proof of your completion for extra credit.
Hat-tip: Farnaz Heidar-Zadeh at Queen’s University, who curated much of this material.