MIT Department of Chemistry
Cambridge, MA 02139
mit.edu email: hzye2011
Year joined: 2015
I manage a personal website here.
|2011 - 2015||B.Sc. in Chemistry||Peking University||Advisor: Hong Jiang|
Mean-field Excited State
Nowadays, the electronic ground states can be computed relatively accurately by correlated quantum chemical methods such as MPn, CCSD(T) and etc. All these correlated methods are built on top of a preliminary mean-field calculation: Hartree-Fock. For excited states, following the same path is somewhat inefficient as the ground state mean-field solution does not have to contain that much of information for excited states. For this reason, many works have been done to obtain mean-field excited solutions directly. Nearly all these methods - including this project - share a common feature: to prevent the solution from collapsing down to the state of lowest energy of given symmetry.
In this project, we develop a new scheme, sigma-SCF, to achieve this goal. By noting that energy variance is local minimum for every state, one might immediately think of variationally optimizing the variance. That won't work in general, however, unless you can guide your program to find the correct local minimum that corresponds to the excited state you're looking for. Our workaround is to use an energy-targeting function, which takes one parameter - your guess of energy to the state in concern - and gives you a good initial guess to that state which can then be fed to your variance-optimizer.
For more details, see our recent publication.