forked from lijiext/lammps
89 lines
2.5 KiB
C++
89 lines
2.5 KiB
C++
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#include "CbPotential.h"
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#include <cmath>
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namespace ATC
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{
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static const double EPS = 1.0e-8;
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// Approximates the derivative of phi
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double CbPotential::phi_r(const double &r) const
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{
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const double dr = r*EPS;
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return (phi(r+dr)-phi(r)) / dr;
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}
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// Approximates the second derivative of phi
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double CbPotential::phi_rr(const double &r) const
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{
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const double dr = r*EPS;
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return (phi_r(r+dr)-phi_r(r)) / dr;
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}
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// Approximates the third derivative of phi
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double CbPotential::phi_rrr(const double &r) const
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{
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const double dr = r*EPS;
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return (phi_rr(r+dr)-phi_rr(r)) / dr;
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}
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// Approximates the derivative of rho
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double CbPotential::rho_r(const double &r) const
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{
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const double dr = r*EPS;
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return (rho(r+dr)-rho(r)) / dr;
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}
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// Approximates the second derivative of rho
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double CbPotential::rho_rr(const double &r) const
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{
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const double dr = r*EPS;
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return (rho_r(r+dr)-rho_r(r)) / dr;
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}
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// Approximates the third derivative of rho
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double CbPotential::rho_rrr(const double &r) const
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{
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const double dr = r*EPS;
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return (rho_rr(r+dr)-rho_rr(r)) / dr;
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}
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// Approximates the derivative of the embedding function
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double CbPotential::F_p(const double &p) const
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{
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const double dp = p*EPS;
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return (F(p+dp)-F(p)) / dp;
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}
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// Approximates the second derivative of the embedding function
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double CbPotential::F_pp(const double &p) const
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{
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const double dp = p*EPS;
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return (F_p(p+dp)-F_p(p)) / dp;
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}
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// Approximates the third derivative of the embedding function
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double CbPotential::F_ppp(const double &p) const
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{
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const double dp = p*EPS;
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return (F_pp(p+dp)-F_pp(p)) / dp;
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}
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// Approximates the derivative of phi3.
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double CbPotential::phi3_q (const double &q) const
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{
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const double dq = q*EPS;
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return (phi3(q+dq)-phi3(q)) / dq;
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}
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// Approximates the second derivative of phi3.
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double CbPotential::phi3_qq(const double &q) const
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{
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const double dq = q*EPS;
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return (phi3_q(q+dq)-phi3_q(q)) / dq;
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}
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// Compute bond angle jik from the squared length of vectors ij,ik,kj.
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double calculate_theta(double ij2, double ik2, double jk2)
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{
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return acos( 0.5*(ik2+ij2-jk2)/sqrt(ij2*ik2) );
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}
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// Initializes atomic interactions for up to three different terms.
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Interactions::Interactions(int a, int b, int c)
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{
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// bitwise OR combines the terms that are listed
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const int abc = a|b|c;
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pairwise = (abc&PAIRWISE)>0;
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embedding = (abc&EAM)>0;
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three_body = (abc&THREE_BDY)>0;
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angle_bending = (abc&ANGLE_BND)>0;
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}
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}
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