We examine the many open questions that arise for nonadiabatic dynamics in presence of degenerate electronic states, e.g., singlet-to-triplet intersystem crossing where a minimal Hamiltonian must include four states (two which are always degenerate). In such circumstances, standard surface hopping approach is not sufficient as algorithm does Berry force. Yet, we hypothesize force may be crucial far creating chiral induced spin separation, now burgeoning field study. Thus, this Perspective...

Abstract Though the concept of Berry force was proposed thirty years ago, little is known about practical consequences this as far chemical dynamics are concerned. Here, we report that when molecular pass near a conical intersection, massive can appear result even small amount spin-orbit coupling (<10 −3 eV), and in turn dramatically change pathway selection. In particular, for simple radical reaction with two outgoing channels, an exact quantum scattering solution dimensions shows...

We demonstrate that, for systems with spin–orbit coupling and an odd number of electrons, the standard fewest switches surface hopping algorithm does not conserve total linear or angular momentum. This lack conservation arises so much from direction (which is easily adjusted) but more generally propagating adiabatic dynamics along surfaces that are time reversible. show one solution to this problem run eigenvalues phase-space electronic Hamiltonians H(R, P) (i.e., depend on both nuclear...

We show that standard Ehrenfest dynamics does not conserve linear and angular momentum when using a basis of truncated adiabatic states. However, we also previously proposed effective equations motion [M. Amano K. Takatsuka, “Quantum fluctuation electronic wave-packet coupled with classical nuclear motions,” J. Chem. Phys. 122, 084113 (2005) V. Krishna, “Path integral formulation for quantum nonadiabatic the mixed limit,” 126, 134107 (2007)] involving non-Abelian Berry force do maintain...

We investigate a spin-boson inspired model of electron transfer, where the diabatic coupling is given by position-dependent phase, eiWx. consider both equilibrium and nonequilibrium initial conditions. show that, for this model, all results are completely invariant to sign W (to infinite order). However, do depend on W, suggesting that photo-induced transfer dynamics with spin-orbit can exhibit electronic spin polarization (at least some time).

Nuclear Berry curvature effects emerge from electronic spin degeneracy and canlead to non-trivial spin-dependent (nonadiabatic) nuclear dynamics. However, such are completely neglected in all current mixed quantum-classical methods as fewest switches surface-hopping. In this work, we present a phase-space surface-hopping (PSSH) approach simulate singlet-triplet intersystem crossing We show that with simple pseudo-diabatic ansatz, PSSH algorithm can capture the relevant make predictions...

We prove both analytically and numerically that the total angular momentum of a molecular system undergoing adiabatic Born-Oppenheimer dynamics is conserved only when pseudomagnetic Berry forces are taken into account. This finding sheds light on nature for systems with spin-orbit coupling highlights how ab initio simulations can successfully capture entanglement spin nuclear degrees freedom as modulated by electronic interactions in limit.

Chemical relaxation phenomena, including photochemistry and electron transfer processes, form a vigorous area of research in which nonadiabatic dynamics plays fundamental role. However, for electronic systems with spin degrees freedom, there are few if any applicable practical quasiclassical methods. Here, we show that two states complex-valued Hamiltonian does not obey time-reversal symmetry (as relevant to many coupled nuclear-electronic-spin systems), the optimal semiclassical approach is...

For a system without spin-orbit coupling, the (i) nuclear plus electronic linear momentum and (ii) orbital angular are good quantum numbers. Thus, when molecular undergoes nonadiabatic transition, there should be no change in total or momentum. Now, standard surface hopping algorithm ignores indirectly equates of degrees freedom to However, even with this simplification, still does not conserve either momenta. Here, we show that one way address these failures is dress derivative couplings...

Excited atomic nitrogen atoms play an important role in plasma formation hypersonic shock-waves, as happens during spacecraft reentry and other high velocity vehicle applications. In this study, we have thoroughly studied collision induced excitation associated with two colliding the N(4S), N(2D), N(2P) states at energies up to 6 eV, using time-independent scattering calculations determine cross sections temperature-dependent rate coefficients. The are based on potential curves couplings...

Within the context of a simple avoided crossing, we investigate effect complex-valued diabatic coupling in determining spin-dependent rate constants and scattering states. We find that, if molecular geometry is not linear Berry force zero, one can significant spin polarization products. This study emphasizes when analyzing nonadiabatic reactions with orbit (and Hamiltonian), must consider how affects nuclear motion-at least gas phase reactions. Work currently ongoing as far extrapolating...

We present a preliminary surface-hopping approach for modeling intersystem crossing (ISC) dynamics between four electronic states: one singlet and (triply degenerate) triplet. In order to incorporate all Berry force effects, the algorithm requires that, when moving along an adiabatic surface associated with triplet manifold, must also keep track of quasi-diabatic index (akin "ms" quantum number) each trajectory. For simple model problem, we find that great deal new physics can be captured by...

The standard fewest-switches surface hopping (FSSH) approach fails to model nonadiabatic dynamics when the electronic Hamiltonian is complex-valued and there are multiple nuclear dimensions; FSSH does not include geometric magnetic effects have access a gauge independent direction for momentum rescaling. In this paper, case of with two states, we propose an extension Tully’s algorithm, which includes forces and, through diabatization, establishes well-defined rescaling direction. When...

We demonstrate that working with a correct phase-space electronic Hamiltonian captures inertial effects. In particular, we show phase space surface hopping dynamics do not suffer (at least to very high order) from non-physical non-adiabatic transitions between eigenstates during the course of pure nuclear translational and rotational motion. This work opens up many new avenues for quantitatively investigating complex phenomena, including angular momentum transfer chiral phonons electrons as...

Nonadiabatic chemical reactions involving continuous circularly polarized light (cw CPL) have not attracted as much attention dynamics in unpolarized/linearly light. However, including (in contrast to linearly) allows one effectively introduce a complex-valued time-dependent Hamiltonian, which offers new path for control or exploration through the introduction of Berry forces. Here, we investigate several inexpensive semiclassical approaches modeling such nonadiabatic presence beginning with...

We revisit a recent proposal to model nonadiabatic problems with complex-valued Hamiltonian through phase-space surface hopping (PSSH) algorithm employing pseudo-diabatic basis. Here, we show that such PSSH (PD-PSSH) ansatz is consistent quantum-classical Liouville equation (QCLE) can be derived following preconditioning process, and demonstrate proper PD-PSSH able capture some geometric magnetic effects (whereas the standard fewest switches approach cannot effects). also find preconditioned...

We investigate spin-dependent electron transfer in the presence of a Duschinskii rotation. In particular, we propagate dynamics for two-level model system which spin-orbit coupling introduces an interstate form $e^{iWx}$, is both position(x)-dependent and complex-valued. demonstrate that systems coupled to Brownian oscillators with rotations (and thus entangled normal modes) can produce marked increases transient spin polarization relative simple shifted harmonic oscillators. These...

Excited atomic nitrogen atoms play an important role in plasma formation hypersonic shock-waves, as happens during spacecraft reentry and other high velocity vehicle applications. In this study, we have thoroughly studied collision induced excitation (CIE) associated with two colliding the N(4S), N(2D) N(2P) states at collisions energies up to 6 eV, using time-independent scattering calculations determine cross sections temperature-dependent rate coefficients. The are based on potential...

We present a novel semiclassical phase-space surface hopping approach that goes beyond the Born-Oppenheimer approximation and all existing formalisms. demonstrate working with correct electronic Hamiltonian can capture inertial effects during pure nuclear translational rotational motion completely eliminate (at least to very high order) non-adiabatic transitions between eigenstates. This work opens many new avenues for quantitatively investigating complex phenomena, including angular...

We investigate the nuclear dynamics near a real-valued conical intersection that is perturbed by complex-valued spin-orbit coupling. For model Hamiltonian with two outgoing channels, we find even small coupling can dramatically affect pathway selection on account of Berry force, leading to extremely large spin selectivity (sometime as 100%). Thus, this Letter opens door for organic chemists start designing spintronic devices use motion and intersections (combined standard coupling) in order...

We revisit a recent proposal to model nonadiabatic problems with complex-valued Hamiltonian through phase-space surface hopping (PSSH) algorithm employing pseudo-diabatic basis. Here, we show that such PSSH (PD-PSSH) ansatz is consistent quantum-classical Liouville equation (QCLE) can be derived following preconditioning process, and demonstrate proper PD-PSSH able capture some geometric magnetic effects (whereas the standard FSSH approach cannot). also find preconditioned QCLE outperform in...

For a system without spin-orbit coupling, the (i) nuclear plus electronic linear momentum and (ii) orbital angular are good quantum numbers. Thus, when molecular undergoes nonadiabatic transition, there should be no change in total or momentum. Now, standard surface hopping algorithm ignores indirectly equates of degrees freedom to However, even with this simplification, still does not conserve either momenta. Here, we show that one way address these failures is dress derivative couplings...