# Faces of HPC: Douglas Rayner Hartree

Douglas Hartree introduced the use of both analog and digital computers to solve a range of complex physical problems algorithmically, such as a numeric solution to Schrödinger’s equation in Physics.

## Introduction

Douglas Hartree was a theoretical physicist, who, after working on anti-aircraft gunnery during World-War I, developed a set of numerical methods to solve complex differential equations of quantum functions, now referred to as the Hartree-Fock approximation.

## Biography

Douglas Hartree was born in Cambridge, England, in 1897. His father, William, was a Lecturer in Engineering at the University of Cambridge and his mother, Eva Rayner, was the President of the National Council of Women and Mayor of the city of Cambridge. He had two younger brothers, who passed away before adulthood.

During school Hartree became interested in Mathematics and later he entered John's College Cambridge. His studies were interrupted by World War I, when he joined a group studying anti-aircraft ballistics. During this time, Hartree gained experience using approximations in complex problems, but solving them on paper rather than computationally. At the end of the war, he returned to his studies and graduated with a Second Class degree in 1922.

A visit by Neils Bohr to Cambridge inspired Hartree to apply his numerical skills to quantum physics. He started a PhD programme under the supervision of Ernest Rutherford. Using Schrödinger's equations and numerical analysis he created his equations of the distribution of electrons in an atom and proposed a solution for them. V. Fock later studied and expanded Hartree’s research, creating the Hartree-Fock equations.

Hartree later visited the United States and saw the building of the first differential analyzer, which performed integration with a wheel rolling on a rotating disk. Returning to Manchester, Hartree built his own differential analyzer machine. When the time came to replace differential analyzers with computers, Hartree advised John Eckert on setting up the ENIAC computer, and demonstrated how to use it to calculate trajectories of projectiles.

*Resources*

*http://www.hpc.cam.ac.uk/historical/people#hartree*

*2http://www-groups.dcs.st-and.ac.uk/history/Biographies/Hartree.html*

*http://www.encyclopedia.com/people/science-and-technology/mathematics-biographies/douglas-rayner-hartree*