Charge distribution described by the density of charge distribution is a basic physical concept. The density of charge distribution is measured by charge density, the amount of electric charge per unit volume of space, in one, two, or three dimensions. More specifically, it can be divided into volume charge density (ρ), surface charge density (σ), linear charge density (λ). Charge distribution can be analyzed quantitatively by evaluating the following parameters: (1) probability of finding a carrier in the core, the shell, and surrounding; (2) the expectation value of the radial coordinate to each individual carrier; and (3) the expectation value of the distance between an electron and a hole.

Figure 1. Charge distribution (Božič, A.L.; *et al*. 2018)

### Application of Charge Distribution

- The local charge distribution of a molecule determines the physical and chemical properties of molecules, such as ionization constant, reaction rate and pharmacophore.
- The charge distribution in a system can help chemistry researchers to investigate the properties of molecules, predict reaction sites,
*etc*. - The atomic charge is also significant for computational chemists, such as calculating molecular descriptors to establish virtual screening models, investigating electrostatic interactions in molecular dynamics simulations, and so on.

### Our Features

- First- and last-passage algorithms

First-passage and last-passage algorithms are two diffusion Monte Carlo methods, and we have developed two methods to obtain charge density on a conducting surface. At Alfa Chemistry, we apply them to compute charge distribution prediction on a conducting object and measure an overall charge distribution.

- First-principles calculation

First-principles calculations are widely used to account for the local electrification of the electrode surface, which often employs fixed ions as counter-charges. We learn the surface electric fields by controlling the counter-charge surface density utilizing first-principles calculation. Our teams can also use first-principles calculations to predict and investigate the physical properties of electrodes, such as mimicking the electrolyte charge density.

- Last-passage Monte Carlo algorithms

We have developed and tested the last-passage diffusion algorithm, a charge-based Monte Carlo algorithm, for the mutual capacitance of a system of interest. We apply the last-passage Monte Carlo algorithms for the charge density on an L-shaped conducting surface. Moreover, our experts can compute charge densities on an L-shaped conductor in 3D space.

Figure 2. Last-passage algorithms (Jang, H.; *et al*. 2021)

### Our Services

Our charge distribution prediction services provide customers with comprehensive data and analysis according to your specific requirements and timeline. Alfa Chemistry can offer you but not limited to the following:

We apply diverse calculation methods to offer accurate electron density predictions. Combined with our powerful machine learning methods, our groups are capable of predicting electronic-structure data of all sizes of molecules varying from small molecules to large compounds, offering detailed information of the exact location of an electron.** **

**QM/MM simulation**

We use a mixed quantum-molecular mechanics formulation to simulate a large biochemical system in which we need to consider solvent effects or chemical reactions included. Moreover, our QM/MM formulation is flexible enough to accommodate almost all QM methods, helping you to accurately and effectively understand the electron correlation effects in QM/MM MD simulations accurately and effectively.

In order to learn the property of electric field energy, we perform electrostatic potential prediction to obtain electrostatic interaction simulations at a molecular level. Our scientists have rich experience in conducting Ab initio methods, Gaussian calculation, and other modeling approaches to provide accurate electronic structure calculations to achieve a fast and accurate prediction.

**Adsorption energy calculation**

At Alfa Chemistry, multiple calculate formation methods are available to calculate the adsorption energy. We provide reliable adsorption data that are accurately measured using various dynamic frontal analysis methods and investigate a diversity of adsorption characteristics.

### Our Advantages

- We are capable of offering safe and economic operation of the distribution prediction to determine target molecular structure.
- We perform searching a large number of all possible charge states for downstream analysis.
- At Alfa Chemistry, various calculation methods and modeling techniques are well designed to provide quantitative predictions of charging stations.

Alfa Chemistry provides fast, specialized, high-quality services of charge distribution prediction at competitive prices for global customers. Personalized and customized service of charge distribution prediction satisfies innovative scientific study demands. Our clients have direct access to our staff and prompt feedback to their inquiries. If you are interested in our services, please contact us for more details.

References

- Božič, A.L.;
*et al*. From discrete to continuous description of spherical surface charge distributions.*Soft Matter*2018, 14, 1149-1161 - Jang, H.;
*et al*. Quadrupole Last-passage algorithm for charge density on an L-shaped conducting surface.*Adv. Theory Simul.*2021, DOI: 10.1002/adts.202100180.