Funding for this research was provided by:
U.S. Department of Energy (DE-AC02-76SF00515, DE-AC02-05CH11231)
DK acknowledges computational resources sponsored by the Department of Energy's Office of Energy Efficiency and Renewable Energy and located at the National Renewable Energy Laboratory.
Received: 6 April 2018
Accepted: 29 May 2018
First Online: 29 June 2018
: The authors declare no competing interests.