Continuous drift-diffusion models are routinely used to optimize organic semiconducting devices. Material properties are incorporated into these models via dependencies of diffusion constants,… (More)

The diffusion quantum Monte Carlo DMC method is the most accurate approach available for calculating the total energies of solids and large molecules.1 Energy gradients are also of great significance… (More)

Atomic force calculations within the variational and diffusion quantum Monte Carlo methods are described. The advantages of calculating diffusion quantum Monte Carlo forces with the 'pure' rather… (More)

Calculating accurate forces within variational and diffusion Monte Carlo (VMC and DMC) methods is a very challenging problem. We derive expressions for the contribution to the Hellmann-Feynman force… (More)

Atomic force calculations within the variational and diffusion quantum Monte Carlo (VMC and DMC) methods are described. The advantages of calculating DMC forces with the “pure” rather than the… (More)

We give an exact expression for the nth derivative of the expectation value of the energy that satisfies the zero-variance (ZV) principle when the wave function and its first n derivatives are exact.… (More)