Cartesian coordinates vectors

Cartesian coordinate vector (x, y, z) Molecular thermal diffusivity Turbulent thermal diffusivity Molecular kinematic viscosity Turbulent kinematic viscosity Karman constant Mass density See Eq. (26)... 

Cartesian coordinates by a canonical point transformation. The Langevin equations, or the equivalent FPEs, for the N coupled atoms are most conveniently written in the 3Af-element Cartesian coordinate vector x = (Xj,..., with conjugate momentum vector p = (p,...,Pjjy),... 

The numerically computed SDP is presented by a set of structures equally spaced along the path where Xi is a Cartesian coordinate vector that includes the... 

The Cartesian coordinate vector in a homogeneous system is expressed as ... 

One says that vectors ai generate the primitive crystal lattice. Magnitudes of vectors aj and angles between them determine a symmetry class of the crystal. It is convenient to consider the crystal structure in Cartesian coordinates. Vectors a are chosen perpendicular to each other, if possible. 

In Eq. (2.4) Jq(s) is the 3x3 inertia tensor, a (s) is the Cartesian coordinate vector of atom i, L (s) is the component of the k normal mode eigenvector on atom i, all evaluated on the reaction path at distance s along it. The higher order couplings, i.e., H2, etc., can be obtained from the general expression for the reaction path Hamiltonian. ... 

A factor-group operation consists of a rotation (a ) and a noninimitive translation (tj [see Slater (1965)]. For the orthorhombic polyethylene crystal of the space group Pnam, symmetry operations are listed in Table IV.l. The symmetry operation R (at the lattice origin) transforms the Cartesian coordinate vector X(g,) as... 

The parameters of this matrix are the image / and the vector d written by [dx, dy] in cartesian coordinates or [ r, 0] in polar coordinates. The number of co-occurrence on the image / of pairs of pixels separated by vector d. The latter pairs have i and j intensities respectively, i.e. 

The empirical pseiidopotential method can be illustrated by considering a specific semiconductor such as silicon. The crystal structure of Si is diamond. The structure is shown in figure Al.3.4. The lattice vectors and basis for a primitive cell have been defined in the section on crystal structures (ATS.4.1). In Cartesian coordinates, one can write G for the diamond structure as... 

Single surface calculations with a vector potential in the adiabatic representation and two surface calculations in the diabatic representation with or without shifting the conical intersection from the origin are performed using Cartesian coordinates. As in the asymptotic region the two coordinates of the model represent a translational and a vibrational mode, respectively, the initial wave function for the ground state can be represented as. 

The elements of these vectors can be evaluated using an off-diagonal fomt of the Hellmann-Feynmann theorem, which in Cartesian coordinates, Xa, is... 

We start by writing the curl equation in Eq. 057) for a vector t(x,y) in Cartesian coordinates. 

The forces in a protein molecule are modeled by the gradient of the potential energy V(s, x) in dependence on a vector s encoding the amino acid sequence of the molecule and a vector x containing the Cartesian coordinates of all essential atoms of a molecule. In an equilibrium state x, the forces (s, x) vanish, so x is stationary and for stability reasons we must have a local minimizer. The most stable equilibrium state of a molecule is usually the... 

The procedure Split selects the internal displacement coordinates, q, and momenta, tt, (describing vibrations), the coordinates, r, and velocities, v, of the centers of molecular masses, angular velocities, a>, and directional unit vectors, e, of the molecules from the initial Cartesian coordinates, q, and from momenta, p. Thus, the staring values for algorithm loop are prepared. Step 1 Vibration... 

The procedure Merge transforms the internal displacement coordinates and momenta, the coordinates and velocities of centers of masses, and directional unit vectors of the molecules back to the Cartesian coordinates and momenta. Evolve with Hr = Hr(q) means only a shift of all momenta for a corresponding impulse of force (SISM requires only one force evaluation per integration step). 

Molecules are usually represented as 2D formulas or 3D molecular models. WhOe the 3D coordinates of atoms in a molecule are sufficient to describe the spatial arrangement of atoms, they exhibit two major disadvantages as molecular descriptors they depend on the size of a molecule and they do not describe additional properties (e.g., atomic properties). The first feature is most important for computational analysis of data. Even a simple statistical function, e.g., a correlation, requires the information to be represented in equally sized vectors of a fixed dimension. The solution to this problem is a mathematical transformation of the Cartesian coordinates of a molecule into a vector of fixed length. The second point can... 

Some of the common manipulations that are performed with vectors include the scalar product, vector product and scalar triple product, which we will illustrate using vectors ri, T2 and r3 that are defined in a rectangular Cartesian coordinate system ... 

Cartesian coordinates, the vector x will have 3N components and x t corresponds to the current configuration of fhe system. SC (xj.) is a 3N x 1 matrix (i.e. a vector), each element of which is the partial derivative of f with respect to the appropriate coordinate, d"Vjdxi. We will also write the gradient at the point k as gj.. Each element (i,j) of fhe matrix " "(xj.) is the partial second derivative of the energy function with respect to the two coordinates r and Xj, JdXidXj. is thus of dimension 3N x 3N and is... 

Field variables identified by their magnitude and two associated directions are called second-order tensors (by analogy a scalar is said to be a zero-order tensor and a vector is a first-order tensor). An important example of a second-order tensor is the physical function stress which is a surface force identified by magnitude, direction and orientation of the surface upon which it is acting. Using a mathematical approach a second-order Cartesian tensor is defined as an entity having nine components T/j, i, j = 1, 2, 3, in the Cartesian coordinate system of ol23 which on rotation of the system to ol 2 3 become... 

The matrix A in Eq. (7-21) is comprised of orthogonal vectors. Orthogonal vectors have a dot product of zero. The mutually perpendicular (and independent) Cartesian coordinates of 3-space are orthogonal. An orthogonal n x n such as matr ix A may be thought of as n columns of n-element vectors that are mutually perpendicular in an n-dimensional vector space. 

The equivalence of the pairs of Cartesian coordinate displacements is a result of the fact that the displacement vectors are connected by the point group operations of the C2v group. In particular, reflection of Axr through the yz plane produces - Axr, and reflection of AyL through this same plane yields AyR. 

These components may represent, for example, the cartesian coordinates of a particle (in which case, n=3) or the cartesian coordinates of N particles (in which case, n=3N). Alternatively, the vector components may have nothing what so ever to do with cartesian or other coordinate-system positions. 

A particle moving with momentum p at a position r relative to some coordinate origin has so-called orbital angular momentum equal to L = r x p. The three components of this angular momentum vector in a cartesian coordinate system located at the origin mentioned above are given in terms of the cartesian coordinates of r and p as follows ... 

The starting point for obtaining quantitative descriptions of flow phenomena is Newton s second law, which states that the vector sum of forces acting on a body equals the rate of change of momentum of the body. This force balance can be made in many different ways. It may be appHed over a body of finite size or over each infinitesimal portion of the body. It may be utilized in a coordinate system moving with the body (the so-called Lagrangian viewpoint) or in a fixed coordinate system (the Eulerian viewpoint). Described herein is derivation of the equations of motion from the Eulerian viewpoint using the Cartesian coordinate system. The equations in other coordinate systems are described in standard references (1,2). 

The divergence of a vector field u, written div u, is given in Cartesian coordinates by... 

Force constant calculations are normally done in Cartesian coordinates. Suppose we have N atoms whose position vectors are Ri, R2,. .., Ra - Each of the atoms vibrates about its equilibrium position Ri g, Ri.e, , R v,e-The first step in our treatment is to define mass-weighted displacement coordinates... 

The set of unit vectors of dimension n defines an n-dimensional rectangular (or Cartesian) coordinate space 5 . Such a coordinate space S" can be thought of as being constructed from n base vectors of unit length which originate from a common point and which are mutually perpendicular. Hence, a coordinate space is a vector space which is used as a reference frame for representing other vector spaces. It is not uncommon that the dimension of a coordinate space (i.e. the number of mutually perpendicular base vectors of unit length) exceeds the dimension of the vector space that is embedded in it. In that case the latter is said to be a subspace of the former. For example, the basis of 5 is ... 

If a vector it is a function of a single scalar quantity s, the curve traced as a function of s by its terminus, with respect to a fixed origin, can be represented as shown in Fig. 8. Within the interval As the vector AR = R2 - Ri is in the direction of the secant to the curve, which approaches the tangent in the limit as As - 0. Tins argument corresponds to that presented in Section 2.3 and illustrated in Fig. 4 of that section. In terms of unit vectors in a Cartesian coordinate system... 

The following important relations involving the ouri can be verified by expanding the vectors in terms of their components i, J and k in Cartesian coordinates ... 

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