3 research outputs found
Discontinuous Galerkin discretization for quantum simulation of chemistry
Methods for electronic structure based on Gaussian and molecular orbital
discretizations offer a well established, compact representation that forms
much of the foundation of correlated quantum chemistry calculations on both
classical and quantum computers. Despite their ability to describe essential
physics with relatively few basis functions, these representations can suffer
from a quartic growth of the number of integrals. Recent results have shown
that, for some quantum and classical algorithms, moving to representations with
diagonal two-body operators can result in dramatically lower asymptotic costs,
even if the number of functions required increases significantly. We introduce
a way to interpolate between the two regimes in a systematic and controllable
manner, such that the number of functions is minimized while maintaining a
block diagonal structure of the two-body operator and desirable properties of
an original, primitive basis. Techniques are analyzed for leveraging the
structure of this new representation on quantum computers. Empirical results
for hydrogen chains suggest a scaling improvement from in
molecular orbital representations to in our representation for
quantum evolution in a fault-tolerant setting, and exhibit a constant factor
crossover at 15 to 20 atoms. Moreover, we test these methods using modern
density matrix renormalization group methods classically, and achieve excellent
accuracy with respect to the complete basis set limit with a speedup of 1-2
orders of magnitude with respect to using the primitive or Gaussian basis sets
alone. These results suggest our representation provides significant cost
reductions while maintaining accuracy relative to molecular orbital or strictly
diagonal approaches for modest-sized systems in both classical and quantum
computation for correlated systems
Establishing the carrier scattering phase diagram for ZrNiSn-based half-Heusler thermoelectric materials
Chemical doping is one of the most important strategies for tuning electrical
properties of semiconductors, particularly thermoelectric materials. Generally,
the main role of chemical doping lies in optimizing the carrier concentration,
but there can potentially be other important effects. Here, we show that
chemical doping plays multiple roles for both electron and phonon transport
properties in half-Heusler thermoelectric materials. With ZrNiSn-based
half-Heusler materials as an example, we use high-quality single and
polycrystalline crystals, various probes, including electrical transport
measurements, inelastic neutron scattering measurement, and first-principles
calculations, to investigate the underlying electron-phonon interaction. We
find that chemical doping brings strong screening effects to ionized
impurities, grain boundary, and polar optical phonon scattering, but has
negligible influence on lattice thermal conductivity. Furthermore, it is
possible to establish a carrier scattering phase diagram, which can be used to
select reasonable strategies for optimization of the thermoelectric
performance.Comment: 21 pages, 5 figure
Cholesterol-Modified Amino-Pullulan Nanoparticles as a Drug Carrier: Comparative Study of Cholesterol-Modified Carboxyethyl Pullulan and Pullulan Nanoparticles
To search for nano-drug preparations with high efficiency in tumor treatment, we evaluated the drug-loading capacity and cell-uptake toxicity of three kinds of nanoparticles (NPs). Pullulan was grafted with ethylenediamine and hydrophobic groups to form hydrophobic cholesterol-modified amino-pullulan (CHAP) conjugates. Fourier transform infrared spectroscopy and nuclear magnetic resonance were used to identify the CHAP structure and calculate the degree of substitution of the cholesterol group. We compared three types of NPs with close cholesterol hydrophobic properties: CHAP, cholesterol-modified pullulan (CHP), and cholesterol-modified carboxylethylpullulan (CHCP), with the degree of substitution of cholesterol of 2.92%, 3.11%, and 3.46%, respectively. As compared with the two other NPs, CHAP NPs were larger, 263.9 nm, and had a positive surface charge of 7.22 mV by dynamic light-scattering measurement. CHAP NPs showed low drug-loading capacity, 12.3%, and encapsulation efficiency of 70.8%, which depended on NP hydrophobicity and was affected by surface charge. The drug release amounts of all NPs increased in the acid media, with CHAP NPs showing drug-release sensitivity with acid change. Cytotoxicity of HeLa cells was highest with mitoxantrone-loaded CHAP NPs on MTT assay. CHAP NPs may have potential as a high-efficiency drug carrier for tumor treatment